US2373560A - Sound recording method and apparatus - Google Patents

Description

April 10, 1945.

J. M. HANERT SOUND RECORDING METHOD AND APPARATUS Filed July 29, 1941 v 8 Sheets-Sheet l NIW.

Num,

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April 10, 1945. J. M. HANERT SOUND RECORDING METHOD AND APPARATUS Filed July 29, 1941 8 Sheets-Sheet 2 WGW..

J. M. HANERT SOUND RECORDING METHOD AND APPARATUS April l0, 1945.

' Filed July 29, 1941 8 Sheets-Sheet 3 April l0, 1945.

J. M. HANERT SOUND RECORDING METHOD AND APPARATUS Filed July 29, 1941 8 Sheets-Sheet 4 April 10, 1945. J. M. HANr- TRT SOUND RECORDING METHOD AND .APPARATUSk Filed July 29, 1941 8 Sheets-Sheet 5 Ljo/z M 'Hauer/Z' v BJ 10M', f 34M@ fifi/,5.

April 10, '1945.

.J. M HANERT soUND RECORDING METHOD AND APARATUS Filed July 29, 1941 r8 Sheets-Sheet 6 April 10, 1945.

J. M. HANERT SOUND RECORDING METHOD AND APPARATUS Filed July 29, 1941 8 Sheets-Sheet 7 April 1o, 1945. J M, HANERT 2,373,560v

SOUND RECORDING METHOD AND APPARATUS Filed July 29, 1941 8 Sheets-Sheet 8 f@ @fo F/LTE/zd 'SMRP /"96g 5K2 :cur oFF new new M/xE/z AMP F/rezz cfg-Agip ZZ BVE 22 40 v ma l l 1 j# y 674 REcoapER Patented Apr'. 10,1945

SOUND RECORDING METHOD AND APPARATUS John M. Hanert, Wilmette, Ill., assigner to Hammond Instrument Company, Chicago, Ill., a. corporation of Delaware Application July 29', 1941, Serial No. 404,487

29 Claims. (Cl. Uil-100.4)

tones of some musical instruments-notably the violin and Hawaiian guitar-is produced by a periodic variation in the pitch ofthe tone at a periodicity of approximately seven cycles per second, although the vibrato rate may be varied between five and ten cycles per second to obtain various effects. If the rate is less than ve cycles per second or more than ten cycles per second, most musicians will consider the effect undesirable. The range of frequency variation in the pitch of the tone necessary to obtain a musically acceptable vibrato effect is from 0.2% to 6.0% of the frequency of the tone; that is, a periodic shift in frequency from 0.1 %v3.0% above to 0.1%,3.0% below the nominal frequency of the'tone. For example, for the note A=440 C. P. S., the frequency variation might be between the frequencies of 439.6 C. P. S. and 440.4 C. P. S. to obtain a very small or "narrow vibrato eifect, while to obtain a large or wide vibrato effect, the frequency variation might be between 426.8 C. P. S. and 453.2 C. P. S. These exemplary limits are not exact, since the listeners determination of what constitutes a pleasing vibrato effect depends upon his musical perception and the mood of the musical selection being rendered.

On the average, a pleasing vibrato effect may be assumed to be obtained by a 6% frequency modulation of the tone at an average periodicity of '7 C. P. S. The frequency modulation should preferably be applied gradually,

Most musical instruments are incapable of producing tones incorporating the vibrato effect. This is to be expected if the instrument is to be easily played on some given pitch. That is, the musical tone generators usually take the form of some stable tuned system, such as a piano stringreed. pipe, and the like. In the case of the piano. the frequencies of vibration of the strings are extremely constant and the musician has no means for imparting a vibrato effect or of 'altering the tuning of the strings while playing. Other instruments of this class navire. no means for intro'iufing vibrato are the chimes. Xylophone, celeste. marimba. and harpsichord. Frtted instruments. such as theguitar, also present little opportunity for the vibrato effect because thel frets more or less limit the number of frequencies possible to the notes of the scale. Likewise, the Woodwinds, orchestral reeds, and accordion produce very little vibrato.

The pipe. organ, ilute, and clarinet fall in a second class of instruments in which the vibrato effect is achieved only in conjunction with a tremulant or intensity modulation, the latter being usually considered monotonous by musicians. That is, the frequency of the pipe can be conveniently shifted only by reducing the wind pressure, which reduction, however, results ina relatively large diminution of sound apart from the frequency shift or vibrato effect.

Another effect, resembling the vibrato, is produced by simultaneously sounding several pipes which are purposely tuned fiat and sharp of the correct pitch to produce a chorus effect. This is also the pleasing effect of several musicians playing a note simultaneously as compared to the note played by a single player.

The reason the vibrato and chorus effects are pleasant probably lies in the fact that more auditory nerves terminating at the basilar membrane of the ear are excited, each however to a lesser degree than in the case of a single loud tone devoid of vibrato and in which the energy is concentrated on but a relatively few frequencies resulting in but a few auditory nerves being violently excited. In other w0rds,'if the music as heard by the listener consists of a great many frequencies, such as provided by vibrato and ensemble tonalties, the ear is less easily fatigued. The many sounds of nature, such as the wind through trees and the sound of ocean waves are particularly pleasant and restful to listen to because of their great audibility, that is, they sound loud, but at the same time do not unduly penetrate or fatigue the ear. Consequently, music in general, becomes more pleasant to hear if a considerable ldegree of vibrato is introduced, which, however, should in no way change the musicians technique in playing standard instruments. In addition, the use of but a few instruments with vibrato added is often l equivalent in musical appeal to many instruments sounding simultaneously without the benefit of 'the vibrato effect.

(A small number of standard instruments with the vibrato effect added produces the same tonal warmth as alarger group of such instruments.)

The vibrato is a very important element in musical expression and its addition tothe tonality at times of emotional climax adds greatly to the musical expressiveness. This is possibly due to the associative fact that the human voice, more or less naturally. has a pronounced vibrato when the speaker or singer is expressing an emotion.` Another application of the vibrato consists in introducing it into poetic and dramatic readings to an extent greater than normally possible with the human voice. Thus, the reading of mystery stories and other exciting selections is greatly enhanced through addition of vibrato at times of emotional stress.

In general, the invention comprises making a recordof the sound in which the vibrato is to be incorporated, picking up a signal from such record' by a pickup which moves relative to the record at a speed varying at vibrato periodicity, ampli` fying this signal, and making a record of the amplied signal. The desired results may be ob-l tained by a variety of slightly diierent methods phonographic method and apparatus for making' sound records incorporating vibrato effects.

A further object is to provide an improved method and apparatus for photoelectrically recording sound modulated to produce a vibrato eect.

A further object is to provide an improved method and apparatus for making sound records.

A further object is to provide an improved method and apparatus for reproducing sound or music in a manner which introduces a vibrato efl'ect.

A further object is to provide an improved means for readily controlling the width and periodicity of the vibrato to be introduced into a sound.

A further object is to provide an improved vibratory motor apparatus which may be easily adjusted as to amplitudeand frequency of vibration.`

A furtherobject is to provide a method and apparatus, whereby a vibrato `of continually varying periodicity may be introduced, so that the listener is not able to detect a definite vibrato rate.

Other objects will appear from the following 4 description, reference being had to the accom- -view of a modified form of the apparatus used to practice the invention;

F18. 14 is a side elevation of simplified form of the vibratory pickup apparatus;

Fig. 15 is a diagrammatic view of modified forms of the apparatus employing a magnetized tape record. l

Fig. 16 is a wiring diagram employing a relaxation oscillator for producing impulses at a vibrato frequency;

Fig. 17 is a schematic diagram of an additional form of apparatus for producing impulses at a vibrato frequency;

Fig. 18 is a schematic diagram of a modiiied recording apparatus in which the vibrato effect is introduced by the cutting head of the recording apparatus;

Fig. 19 is a diagrammatic view of a modified form of the invention,in which the vibrato may selectively be made more or less eiective on the high or the low frequencies of the sound transmitted; and,

Fig. 20 is a schematic view of a modified form of the invention, in vwhich the vibrato modulating frequency is manually introduced.

In Fig. 1, the apparatus for introducing the vibrato eiect is illustrated as comprising a phonograph motor mounted on a suitable base 3| and driving a turntable 32 at the customary speed. The turntable carries a record A, which is a recording of the music or sound into which -so that the operator of the Iapparatus may listen Figs. 3 and 4 are similar views of modied inFig.9;

Fig. 12 is a central vertical sectional view of a further modification of the apparatus for producing vibrato variations in the speed of the turntable;

to the sound as it is being recorded. The tone arm 42 carrying the pickup 34 is mounted upon a resilient support 44,.which is preferably resilient in itself and is imbedded in a base 46 of sponge ru'bber or the like. The base 46 is carried by a bracket 48, which is mounted for oscillation on a bearing 50 carried by the base 3I,-this pivotal mounting of the bracket 48 being provided so that the tone arm may swing to follow the groove in the record.

A driver 52 is preferably in the form of an electric vibratory motor,rsuch as the motor portion of a dynamic loud speaker, and has its moving part connected to the tone arm 42 .by a cord or wire 54. The driving motor 52, especially if it is in the form of the motor of a dynamic loud speaker, is responsive to even minor variations in the frequency and amplitude of the energizing current supplied thereto, and for this reason, may

Fig. 13 isa diagrammatic view of apparatus be considered as a synchronous vibratory motor.

In order to produce a record having its various sound frequencies modif-led at a vi-brato rate and to a vibrato extent, it is necessary to supply current to the driver 52 at a vibrato frequency and at a voltage determined by the width of the vibrato frequency shift which is desired. 'I'he means for supplying the energizing current for the driving motor 52 is illustrated in Fig. 1 as comprising a disc 56 having a plurality of notches 51 in its periphery. These notches are not necessarily accurately spaced along the periphery, but on the contrary, are preferably spaced rather irregularly. The disc 56 is driven by an adjustable speed motor 58 (which may include a speed-reducing gearing), and the speed of the motor is adjustable by means of a rheostat 60. Assuming uw; une disc ss has twelve notches t1, as shown,

the speed of the disc should preferably be ad- A .instable between 20V and 50 R. P. M. Within this range of adjustment, the notches 51 pass a stationary point at a rate of four notches to ten notches per second.

A suitable continuous light source 62 is located above the disc 55 'in position to project rays of light through the notches 51. Beneath the disc 55 is located a shutter 64 mounted in suitable guides 66 and biased to move to a position shutting off the light, rays passingthrough the notches 51, by a pair of tension springs 68. A photocell 10 is positioned beneath the shutter 64 so as to have the amount of light reaching it from the source 62 controlled by that passing through the notches 51 and past the shutter 64. The shutter is adapted to be manually operated by any suitable means, such as a cord 12 attached to it.

The output of the photocell 10 is supplied to a preamplifier 14, the output of which .is in turn connected to a low-pass filter 1B and power amplifier 18 and supplied as the energizing current for the driving motor 52. The low-pass filter circuit 16 is preferably made to pass all frequencies below 10 C. P.' S. without appreciable attenuation and to cut off all frequencies 'above this value.

It will be understood that the phototube will be'enclosed in a suitable housing so that it will be affected only by the light reaching it through ythe notches 51 and passing the shutter 64.

In operating the apparatus of Fig. 1, the potentiometer 60 is adjusted to cause the motor 58 to operate at the desired speed, and after placing the record A upon the turntable 32, the needle of the pickup is placed upon the record. The sound recordedon the record will be heard by the operator from the speaker 40, and as a phrase or sentence in the musical selection is reached which lacks vibrato, the operator will pull-the cord 12 to operate the shutter 64 to the extent desired.

so related to the compliance of the supporting" members 44 and 46 that the tone arm will have a natural frequency of vibration generally within the vibrato frequency range, i. el., from 4 to 10 C. P. S.

The frictionv of the needle on the record and the damping effect of the sponge rubber support 46 tend to reduce the Q of the vibratory portion of the apparatus so that the tone arm may readily he made to vibrate throughout the range from 4 to 10 C. P. S. without the necessity of utilizing an excessively powerful driver. Furthermore, the

friction of the needle on the record and the internal friction of the support 46 are effective rapidly to damp vibration of the tone arm assembly so that the tone arm. will quickly come to rest upon discontinuing the supply of energizing electrical impulses to the driving motor 52.

' Because of the provision of this low-pass filter I j 1.6, the light source 52 may be energized with improved result of my invention is obtained mere- Since the extent of opening of the shutter 64 determines* the amplitude of the electrical impulses delivered to the driving motor 52, it will determine the width of the vibrato effect introduced. It will be understood that as the pickup 34 is os-l cillated by the vibratory driver 52, its speed of motion will be periodically varied, relative to the record A, and due to the Doppler effect, the electrical signal produced in the pickup 34 will periodically vary with respect to the frequency of the sound on the record A being picked up.

This frequency modulated sound is, by means of the recording apparatus 38, recorded on ya new record which serves as a. master record from 'which commercial impressions may be made in the well known manner.

Thus, by operating the shutter control cord 12 and the rheostat 60, .the operator may control the periodicity of the vibrato modulations introduced and also control the extent or frequency range of the vibrato, and he may introduce the vibrato arm 42 and parts carried thereby is preferably ly by amplifying and translating into sound the electrical impulses produced in the pickup 34, without re-recording the sound.

The apparatus shown in Fig. 2 is in general principle similar. to that shown in Fig. l, and

corresponding parts of the system are therefore ,Y designated by the same reference characters as l used in connection with Fig. l, although some of the parts of the system are illustrated in greater detail.

In the system of Fig. 2, the driver 52 is illusy trated as comprising a permanent magnet dynamic speaker motor, including a voice coil 80 wound on a form 82 which is connected to a ilexible supporting spider 84, the spider being connected by a cord 54 with the resilient support 44 for the tone arm 42. The recording apparatus is illustrated as comprising a recording amplifier 86, the output of which is supplied to the cutter head 88 of the recording apparatus 90, carrying a record blank B upon which the sound as modulated by the vibrato apparatus is to be re-recorded.y

The voice coil 86 derives its power from a variable frequency oscillator 92, the frequency of oscillation of which may be varied by a suitable control`94 for manual adjustment of the frequency and the frequency of which may be periodically varied by a periodic frequency shifter 98. Assuming that the variable frequency oscillator is one in which a variable capacity is employed to determine its frequency, the frequency control 94 may comprise merely a variable condenser in parallel with the tuning capacity of the oscillator, while the frequency shifter 96 may comprise an additional variable condenser in shunt with the tuning condenser of the oscillator provided with means for cyclically varying its capacity.

'Ihe outputl of the oscillator is fed to a suitable intensity control device 98 having, in addition to its manually adjustable controlling elements, a variable resistance |00, the moving contact of which is connected to a pivot shaft |02 secured to the frame 48. Thus, as the needle of the pickup 34 approaches the center of the record A and the lineal speed of the record with respect to the pickup needle decreases, the amplitudes of the impulses delivered by the variable frequency oscilany desired frequency between 4 and 10 C. P. S.,

but due to the periodic frequency shifter 96, the vibrato periodicity is notv maintained constant, but changes gradually, thus overcoming the musical disadvantage of having the vibrato always at the same periodicity. The provision of the tunable oscillator instead of the photoelectric system of Fig. l as a source of electrical impulses for energizing the driving motor 52, results in a reduction in cost of the apparatus without materially interfering with the extent of control which the operator has over the -width and frequency of the vibratomodulation.l

The apparatus shown in Fig. 3v is generally similar to that of Fig. 2, the lcorresponding parts bear the same reference characters. I'he essential ydifference in the apparatus is that the bracket 48 has an extension |06 carrying a motor |08 (which mayinclude a suitable gear speed reduction), the motor being connected by a belt with a suitable pulley I2. The pulley I2 is provided with a plurality'of holes ||4 spaced difyferent distances from the center of the pulley,

which are adapted to receive a pin ||6. The pin 6 has one end oi' a belt |20 swiveled thereto, thebelt passing over an idler pulley |22 and having the other end connected to the tone arm 42 and its support 44. The speed of the motor |08 may be varied b y a manually adjustable rheostat v tensioned member |34 attached to the tone arm 42. The electromagnet |28 is energized from a generator |36 which is driven by a motor |38,

the speed of which is controlled by 'a rheostat |40. .50 The moving contact of the rheostat |40 is connected to a worm wheel |42 so as to move therewith, the worm wheel being rigid with a pin |44 to which the lower end of the tensioned member |34 is connected. The worm wheel is adapted to be rotated in either direction by a manually adlustable worm |46.

Thus, asthe speed of the motor |38 is increased by adjustment of the rheostat |40, the tension on the tensioned member |36 isv simultaneously increased'so that the tone arm 42 and 'parts moving therewith, together with the tensioned member |34, form a broadly tuned mechanical systeni, the natural frequency of vibration of which me, mi, and 52, shown diagrammaueauy in Fig. 2.

'I'he oscillator may comprise a pair of pentodes |60, 16|, connected in push-pull with their frequency of oscillation determined by the resonant frequency of a mesh comprising inductance Ll and condensers CI, C2, and C3, the condenser C serving as the primaryA frequency determining condenser, while the condensers C2 and C3 are adapted to be connected in parallel with the condenser CI by the operation of a switch |62, thereby to vary the frequency of oscillation of the oscillator.

A further means for periodically shifting the frequency of oscillation of the oscillator |50, comprises a reed |54 (having a natural frequency of oscillation in the order of 3 C. P. S.) suitably maintained in vibration by a driving electromagnet |56 -in the well known manner, the reed |54 carrying an insulated contact plate |58 which is adapted to complete a circuit through an inductance L2 to connect the latter in parallel with the inductance Ll. The periodic frequency shift- .ing circuit may be rendered inoperative byopening a switch |60.

The oscillations generated in the tubes |50, |5| and associated circuits are supplied in push-pull to the grids of triodes |62, |63, which are resistance coupled to ampliiier tubes |64, |65, while .with a pair of push-pull control tubes |66, |61. 'Ihe grids of the tubes |66, |61 are normally biased substantially to cut off through a resistor RI which connects the center tap |69 of the secondary of transformer A'Ifl to a point of fixed negative potential indicated as -50 v., a suitable biasing voltage for the control tubes |66 and |61, assuming that the latter are tubes of the 6K7G e type. The negative bias on the tubes |66, |61 may be decreased by closure of a switch |68 which connects the center tap |69 to a terminal of constant direct current potential, indicated as -5 v. With apotential of -5 volts on the grids of tubes |66,

|61, they will transmit the impulses of the oscil- A lator.

Occasionally it is desired to have the music modulated by the vibrato frequency for only a short interval, and to accomplish this purpose, there is provided a'key |10 which is adapted to connect a normally charged condenser C4 to the 'center tap |69, the-size of the condenser C4 determining the duration of the interval through which the control tubes will be .rendered conductive and hence the interval through which the vibrato modulation (as will hereinafter appear) is eiective.

Additional condensers C5 and C6 are adapted to be connected in parallel with the condenser C4 by manual operation ofswitches |12 and |13, respectively. It will be noted that condenser C4 (as well as condensers C5 and C6, if the switches |12 and |13 are closed) are adapted to be charged from the terminal ,-5 v. through a resistor R2 when the key |10 is in its undepressed position. The outputs of the control tubes |66, |61 are resistance capacity coupled in push-pull manner with power amplifier tubes |14, |15. tiometer |16 shunts the input of the power am- 70 pnfier tubes |14 and |15 and is adapted-to be operated by a manual control knob |18, the knob being normally biased by a torsion spring |80 to move in a counterclockwise direction to the maximum extent, thereby to cause the complete shunting of the input to the power tubes n4, ne and the latter are coupled through a transformer TI` A potencut off the transmission of the oscillator signals thereto.

. Whenever the vibrato effect is desired, the control knob |18 is moved clockwise, thereby to connect agreater or" lesser portion of the potentiometer resistance |18 across the Iinput circuitsv of the tubes |14, |15. Release of the control knob will immediately result in cutting oi the signal. The output of the power tubes 14, |15, is coupled through a transformer T2 with the rmotor 82.

driIr'ieorder further to control the amplitude of the signal transmitted to the driver 52 in accordancel with the distance of the needle from the center of the record, a potentiometer |82 is connected across the primary of the transformer T2 and. by the position of the sliding contact therefor, determines the amplitude of the energizing signal for the driver 82. The sliding contact of potentiometer |82 may be physically connected to (but electrically insulated from) the pivot shaft of the tone arm carrying frame 48, as shown, for example, in Fig. 2.

The oscillator of Fig. 5 is illustrated as representative of any suitable source of electrical lmpulses oi vibrato frequency in which the frequency may be easily controlled, may he periodically shifted, and in which the amplitude may be controlled in various ways to produce a transitoryl increase in amplitude of the signal or to produce any desired sustained signal amplitude.

The apparatus shown in Fig. 6 constitutesy a simplification of that previously described, including a driver 52, which may be supplied with electrical impulses at vibrato frequencies by any suitable means, previously or hereinafter to be described, the tone arm 42 vibrated by the driver 82 having its pickup cooperable with the record A mounted on the turntable 32, which is detachably secured over the top of a spindle |88, the spindle also carrying a turntable |88 upon which rests the record blank B.

The recording head 88 is supplied with the signal picked up by the pickup 34. amplified by the pre-amplifier and power amplifierv |88, which latter also supplies the monitor speaker 40. The spindle |88 is driven at a constant speed through a worm wheel |80 meshing with a driving worm |82.

A further modified `form of apparatus is shown in Fig. '7 as comprising a non-'vibratory pickup 34 and tone arm 42 cooperating with a record A carried by a turntable |84 which is mounted for oscillation on a rotating shaft |88 driven by a worm |81 and worm wheel |88. A torsion coil spring 200 has one end anchored to the turntable |84 and its other end anchored to the worm wheel |88. The worm wheel |88 hasa cam 202 formed thereon, this cam preferably having downwardly extending camming projections spaced somewhat irregularly. For example, assuming that the nor-` mal speed of rotation of the turntable |84 is 78.0 R. P. M., five cam projections may be provided on the cam 202 spaced apartangular distances as follows: 68, 73, 67, 78, and 74,

A follower roller 204 is cooperable with the cam 202, the roller being carried at the end of a lever 208 pivoted at 208 and biased by an adjustable compression spring 2|0 to hold the roller 204 in engagement with the cam surface. The lever 208 vhas an upwardly extending arm 2|2 carrying a braking shoe 2|4 of feltlea'ther, or similar material, the shoe being cooperable with a friction ring 2|8 secured on the lower surface of the turntable |84.

Thus, as the worm'gear |88 rotates, the cam 202 oscillates the lever 208 periodically to bring its brake shoe 2| 4 into momentary engagement with the friction ring 2 8 and thus momentarily slightly retard the turntable |84. The rotary movement of inertia of the turntable |84 and parts carried thereby is so related to the resilient torque of the .spring 200 that the normal frequency of oscillation of the turntable with respect t0 the constantly rotating shaft |88 will be in the order of 7 C. P. S. Such oscillation is relatively rapidly damped due to the friction imparted by the needle in thengroove of the record as well as by the friction at the bearing of the turntable |84 upon its In the embodimentsof the invention shown in Figs. 8 to 12 inclusive, the turntable is resiliently coupled to its worm wheel 220 by a torsion spring 222, and thus theturntable 32 will oscillate relative to the drive shaft 224 whenever the latter is accelerated or retarded.

In Fig. 8, the worm wheel 220 is driven through suitable gearing by a motor 228 which is preferably of the synchronous type energized by current from a variable frequency source 228 which may be, for example, a variable frequency osc llator land amplifier of the general type shown in Fig. 5,

and also provided with a `frequency shifting apparatus 23|).` The oscillator may be adjusted to oscillate at a desired mean frequency, such as 6 C. P. S., while the frequency shifting apparatus 230 will operate to vary the frequency generated by the oscillator amplicr 228 between limits above and below 6 C. P. S., such as, for example, 5.5 and 6.5 C: P. S.

' The resultant changes in the speed of the driving motor 228 will be reflected in oscillation of the turntable 32 relative to its drive shaft 224, and for this reason, the spring 222 is so chosen that its compliance will be of a value causing the turntable to have a natural frequency of oscillation relative to its drive shaft in the order of 6 C. P. S.

Since the changes in speed of the motor 228 are not very accurately and directly reflected in changes in the speed of movement of the turntable 32, a simplified means for causing such oscillation of the turntable and its shaft may be provided. Such more simplified apparatus is shown in Fig. 9, wherein, the driving motor 232 may be of a type in which the speed varies with impressed voltage and current is supplied through a variable resistance 234, a selected portion of which may be periodically shunted, at a vibrato rate (by a circuit including a switch 238 closed by a. cam 238 driven from any. suitable mechanism, preferably o 'ne which provides means .for varying the speed of the cam 238).

In both Figs. 8 and 9, the pickup 34 an'd tone arm 42 may be of conventional construction and mounted on a pivot in the usual manner.

In Figs. 10, 1l, and 12, is disclosed a further modified form of turntable drive by which vibrato oscillations ofthe turntable relative` to its drive shaft may be obtained. In each of these, the turntable is driven by a synchronous or constant speed motor 228, as in the construction of Fig. 8.

In Figs. 10 and 11, the turntable 32a is provided with arcuate segmental flanges 240 projecting from its periphery. These segmental fianges are preferably spaced irregularly about the turntable -and are adapted to pass between the poles of a I table anges 24a are made of soft steel or other 1 magnetic material. In this apparatus, asin those of'Figs. 8 and 9, the pickup @t and tone arm :i2 are pivotally mounted in the customary manner.

In Fig. 12,` the apparatus is generally the same as that of Figs. and 11 except that an electromagnet 252 held in xed position has been substituted for the permanent magnet. The turntable 32a may be of the same construction as shown in Figs. 10 and 11, assuming that the electromagnet 252 is energized by direct current. If alternating current is used to energize the electromagnet, the segmental flanges 220 are preferably made `of copper or aluminum so as to provide a braking torque due to eddy current losses as the flanges 260 pass between the poles of the electromagnet 252. Whether energized by alternating or direct current, the effectiveness of the electromagnet 32 may bevaried by a rheostat 252.

As an alternative construction, the turntable may be provided with a continuous ange passing between the poles of the electromagnet 252, and the electromagnet energized by alternating current of relatively high frequency modulated substantially 100% by a vibrato frequency.

In each of the constructions of Figs. 8 to 12 inclusive, the electrical vibrations produced in the pickup are amplined and supplied to a monitor speaker and a recording apparatus for making a master record of the vibrato modulated sound.

In Fig.` 13, is disclosed an apparatus suitable for introducing the vibrato effect in sound on lm records. The apparatus comprises a platform 256 which is connected to a fixed support 258 by a leaf spring 260. The platform 256 carries a light source 262 and a lens system 264 for forming the light from the lamp 262 into a narrow beam for scanning a sound record ona film 266, the film being driven at constant speed by any usual means. The beam of light as modulated by the record on the nlm 226y falls upon a photo cell 268, the output of which is amplied by amplier 210 and supplied to a monitoring speaker 212 and to a recorder 218. The recorder 276 may be one vfor recording sound on i'llm or recording it on a phonographic record.

In order to produce a vibrato eect in the ysound re-recorded or as it is heard from the monitoring speaker 212, the platform 256 is oscillated by'a driver 216 of any suitable construction, such as ythat, previously described, the driver vbeing energized by an oscillator and amplifier 218, which may be'of the construction shown in Fig. 5; and having suitable controls for varying the frequency and amplitude of its output. thereby to vary the frequency and amplitude of oscillation of the platform 256.

Since the means for moving the lm 266 is supilar to some of the modications previously described, andf corresponding reference characters have therefore been applied to the parts which are identical with those previously described. In

this construction, the tone arm 02 is pivotally secured to the upper end of a relatively rigid support 280. The lower portion of the support 266 is imbedded in a cushion 282 made of sponge rubber or the like which is elastic and yet aiords suflicient mechanical resistance to oscillation of the support 280 as to damp such oscillation rapidly.

Fig. 15 illustrates an apparatus for use in produclng sound-directly, as for broadcasting purposes, jor making a record of sounds from a plurahty of sources, in which some sounds are vibrato modulated and others are not. Forv example, in broadcasting or recording the music produced by a large orchestra, it may be desirable to add a vibrato eiect to the music produced by one section of the orchestra, the instruments of which are incapable of producing a vibrato, While it may not be desirable to add a4 vibrato effect to the music produced by other sections of the orchestra, such as the string section, since the music produced by such section will already contain an ample vibrato.

11n. Fig. i5, a microphone 290 is provided for picking up sounds to which it is desired to add a vibrato, while a microphone 29| is provided for sounds already containing a vibrato or sounds which would not be improved by the addition of the vibrato eifect. The signal picked up by the microphone 290 is amplied byy an amplifier 292 and supplied to a recording electromagnet 290 which is cooperable with a hardened steel band 296 secured to the periphery of a circular wheel 298. The wheel 298 is rotated at constant speed by any suitable means. The recording of the sound on the band 296 is accomplished electromagnetically in the manner of the telegraphone. A magnetic pickup 300 is carried by an arm 302 pivoted on the shaft of the wheel to the modulator andradio frequency amplifier 3l@ of a radio broadcasting transmitter or to the amplier 86 of a recorded 88, 90, depending upon the operation of a pair of switches 3|2, 3| 3. A

wiper magnet 3M is xed beyond the pickup 30|! and is effective to erase the signal magnetically recorded on the band 296. Depending upon the position of the pairs of switches 3|6, 3|8, the signal picked up by the microphone 29| may be fed either to an amplier 320 or 322. With the switches 3| 6 and 3| 8 in the position shown in the drawings, the signal is supplied to the amplifier 320 and thence to a recording electromagnet 324 so that the signal from the microphone 29| is recorded -on the magnetizable band 296 and may be picked up by a magnetic pickup 326 which quite lof controls 328 and 329 on the mixer paneL366,

the relative amounts of the signals from the pickups 300 and 326 may be readily controlled.

When the switches 3|6 and 3I8 are moved into opposite position from that in which they are shown in the drawings, the signal picked up by the microphone 29| is fed directly to the amplifler 322 and thence to the mixer 306. This signal will be slightly ahead (in point of time) ofthe signal derived from the pickup 360, but in certain circumstances, such lead of one signal over the other is desirable.

Thus, by the use of the apparatus of Fig. 15, multiple sources of sound or music may have a vibrato added'thereto or not, as desired, and the sounds recombined into a single composite signal, which may beamplied and recorded, broadcast, or heard through a speaker system.

Fig. 16 discloses a generating system which may be used in place of the apparatus shown` in Fig. 5. The generator comprises an oscillator tube 332, which is preferably a gas triode of the 885 type. The oscillator is of the relaxation type, in which a condenser C8 is charged through a timing resistor RI connected to a suitable source of direct; current potential, such as +300 v. The oscillator is oscillated at a frequency determined generally by the values of the condensers C8 and RIU, but its frequency may be adjusted by means of a variable self-bias resistor RII. This oscillator is preferably adjusted so as to oscillate at a frequency of approximately 6 C. P. S. The bias on the tube 332 is determined not only by the self-bias `resistor RII, but also by the potential of a terminal 334, which is connected to the grid of the tube 332 by a protective resistor RI2.

The potential at, the terminal 334 varies periodically at a frequency of approximately 1 C. P. S. due to its connection through a blocking condenser C9 and filtering resistor RI4 with the output circuit of an oscillator tube 336, which may likewise be a gas triode of the 885 type. The oscillator, including the tube 336, may be of the same construction as .that including the tube 332 except for thevalues of the circuit constants, these being so chosen as to cause the oscillator tube 336 to operate at a frequency of approximately 1 C. P. S. The output of a relaxation oscillator of the type illustrated is of generally saw-tooth wave shape, and to change this output wave into one more nearly sinusoidal, the filtering resistor, together with a condenser CII), forms a mesh, most effective to transmit frequencies in the order of 1 C. P. S.

The terminal 334 is connected to ground through a lgrid resistor RIS of relatively high value. The resistors RIG and RIZ determine the normal bias, in effect forming a variable bias determining network for the .tube 332, the fixed adjustable bias being controlled by the variable resistor RI I.

As a resultof the one-cycle variation in grid bias on the oscillatortube 332, its frequency of oscillation will vary each second through frequencies between 5.5 and 6.5 C. P. S. The output signal of the oscillator tube`332 is of saw-tooth wave shape and in order to change the wave shape to one substantially sinusoidal, filtering resistors RI8, RIS, and condensers CI2 and CI3 are provided in the output circuit, which is coupled to the input circuit of an amplier tube 340 by a blocking condenser CI4. The primary of a transformer Tl corresponding to the correspondingly numbered transformer of Fig. 5, is connected in the plate circuit of the ampli'er tube 340. The output circuit beyond the transformer TI may be identical with that shown in Fig. 5. A

It will thus be seen that by the use of the circuit of Fig. 16 impulses continuously varying in frequency between 5.5 and 6.5 C. P. S. (or comparable values) may be supplied for the operation of the driving motor used to vibrate the pickups 34 or other elements to be vibrated at a vibrato rate which are employed in the various modid forms of the invention.

Another form of vibrato frequency generatmg system is shown in Fig. 17, in which a random noise generator 342, which may be of any suitable form, such as an electrical signal derived from a random noise phonograph record, or may be the electrical/equivalent of noises, such as the breaking of ocean waves, the crackling of a ilre, or the electronic noises of an unexcited vacuum tube circuit, etc.

The output of the noise generator 342 has its amplitude controlled by an attenuator 344, and is supplied to a. ltering apparatus 346, which may include a tunable inductive reactance filtering mesh 348, which is tuned to pass frequencies in the order of 6 C. P. S. The frequency passed by the filtering apparatus 346 may be controlled by a periodic frequency changer 350 connected to vary the resonance peak of the lterlng mesh 348. The output of the filtering apparatus 346 is supplied to a power amplifier 352 and the amplified impulses utilized to energize the vibratory driver 52 utilized Y in the various forms of the invention.

Because of the random character of the original frequencies supplied by the generator 342, the output of the ampliiier 332 will vary in frequency throughout a limited range (depending upon the sharpness of the resonance peak of the filtering mesh 348), and as a result, a vibrato determined by this 'output frequency will be veryirregular and not berecognized as a periodic variation in the frequency, but instead, will be heard as a fullness 'd and richness of the tone produced.

The apparatus illustrated in Fig. 18 is designed for direct recording of a vibratoless sound in a manner such that the recorded sound will contain the vibrato. In this figure, the sound is picked up by a microphone 354 and amplified by an amplifier 356 and supplied to a monitoring speaker 40, as well as to the cutter head 358 of a 00 recording apparatus. The cutting head is vibrated by means of a power driver 52 supplied with impulses of a varying vibrato frequency,'as might be obtained from the photoolectric pulse generator 360 (as shown in Fig. 1). Itis, of course, essential that the pulse generator 360 is provided with sumcient amplification that the driver 52 may be vibrated smoothly so as to not cause distortion in the record sound due to irregularities in the resistance to movement relative to the record offered by the cutting stylus of the head 358. Thus, the

original master record of a musical production could be made to incorporate a vibrato not present in the music as produced.

Generally speaking, a vibrato eilect is more 'desirable intones in the higher frequency range than in the low frequency, especially bass, ranges. In order to make it possible to dub" a record vfrom a record of music not containing suicient 36d. The pickups 36a and 3th carried by tone'- arms 32a and @2b cooperate respectively with the two records A, and each of the tone arms is adapted to be vibrated in any one of the numerous ways previously described. The operation of the vibrating mechanisms for the tow tone arms is preferably independent and independently controllable.

The signal picked up by the pickup 3de is supplied to a filtering mesh 366, while that derived from the pickup @t3 is supplied to a filtering mesh 367. The filtering mesh 36S is a high-pass filter, sharply cutting off all frequencies below 250 C. P.. S., while the filter 367 is a low-passl filter, sharply cutting of all frequencies above 250 C. P. S. The output of the filters 36S and 367 is supplied to a mixer 368 having controls 37u and 3H, by which the relative amplitudes of the si-gnals from the filters may be regulated and the combined output of the filters supplied to an amplifier 372. The signal from the ampliiier 372 is supplied to the cutting head of a recorder 37d.

In operatingthe apparatus of Fig. 19, two identical records are placed upon the turntable, (the shaft 362 is sectionalized to permit .the insertion of the lower record), the records being so placed on their turntables that the sound tracks thereon start at the same angular position. The needles of the pickups 3e having been placed in the corresponding grooves of the two records, the rerecording may be commenced, -the operator controlling the frequency and extent of vibration of the pickup Bda to produce the most desirable musical result. Such introduction of vibrato, due

to the iilter 356, will be'eilective substantially' exclusively upon frequencies above 250 C. P. S.

Ordinarily, thevibrating mechanism for the pickup Sb will not 'be energized, but in the event that for special musical purposes a vibrato is desired on .the frequencies below 250 C. P. S., the vibrating driver vfor the pickup 35h may be energized, and in such instances that both pickups 35a and Stb are vibrated, they are preferably vibrated at slightly different frequencies and usually with the vibration of the pickup 3th of less amplitude than that of the pickup 34a.

In Fig. A20 is illustrated a very simple form of apparatus for` introducing a vibrato effect in sound being re-recorded. In this ligure, the tone arm 42 is mounted upon la. flexible resilient support 380 imbedded in a sponge rubber `cushion 382. A flexible band or tape 384, such as a cloth ribbon, has one end secured to the tone arm i2 and its other end anchored to a base 38B. The upper surface of the base 386 has'a layer 388 of felt or the like.

The output of the pickup 3d is supplied, as in most of the previously described forms of the invention, to an amplifier 36, monitoring speaker 4U, and a recording apparatus 86, 90. Whenever, in the re-recording of a musical selection from the record A, it is desired to introduce the vibrato eiect, the operator will merely press vupon the'band 386 periodically at a vibrato frequency rate, thereby vibrating the pickup 3d and tone ann E2.

By moving his finger downwardly toward theanchored end of th tape 38d, the operator may very readily control the amplitude of the vibration imparted to the pickup 3c, whereas, when the band 3ft is engaged toward the center thereof, the amplitude .of the vibration, for a given finger pressure, will be at a maximum. The apparatus of Fig. 20 thus forms a very simple and effective means for vibrating the, pickup to cause intro duction oi' the vibrato effect in the music being re-recorded.

In the various forms of vibrato introducing apparatus disclosed herein, it will be apparent that the vibrato modulated sound may be listened to directly from speakers, may be transmitted to a radio broadcast transmitter, or may be rerecorded upon a master record, from which other commercial records `may be produced. The apparatus is principally designed for the manufacture oi records of improved musical characteristics due to the artistic introduction of the vibrato effect. As previously indicated, the degree of the skill of the operator of the apparatus will, in a. considerable measure, determine the effectiveness of the method of making lthe vibrato modulated sound records. However, even a relatively unskilled operator, with the simple .form of apparatus disclosed herein, will be able very materially to improve the musical attractiveness of recorded sound, provided he adheres to the relatively simple principles involved. The vibrato effect should preferably be employed intermittently in the appropriate portions of the musical selection for the purpose of introducing richness and fullness in the tones and variety in the overall musical eiect.

While I have shown and described a number of different forms of my invention and a number of dierent methods by which the desired results of the invention may be obtained, it will be apparent to those skilled in the art that other modications and variations of the apparatus and method may be made without departing from the underlying principles of the invention. I therefore desire, -by the following claims, to lnclude within the scope of my invention, all such modifications and variations by which substany tially the yresults of my'invention may be obtained by the use of substantially the same or equivalent apparatus and methods.

I claim: I

1. The method o-f recording sound upon a record by a, recording means supplied with the sound as electrical impulses which includes the step of relatively moving the recording means and record at a speed represented by a constant speed modified by acceleration and retardation at a periodicity in the order of '7 C. P. S.` and to an ex tent such that the mam'mum and minimum relative speeds will be between..l% and 3.0% above and =below the normal speed respectively.

2. The method of making a sound record which comprises, translating mechanical sound vibrations into electrical impulses while modulating the electrical impulses at a vibrato rate and to the extent of a musical vibrato, and making a record of the modulated electrical impulses.

3. In a Vsound recording apparatus, the-combination of a rst sound record, means to move said record at a constant speed, a pickup cooperable with said iirst record for translating the sound vibrations recorded thereon into electrical impulses, ya compliant support for said pickup, a driving motor for vibrating said pickup in the direction of the constant speed relative move-A ment between the pickup and first record, 'means associated with said motor for varying the speed and amplitude of vibrations transmitted from said motor to said pickup, and means fo'r producing a secondsound record of the electrical impulses generated by said pickup.

4. In a sound recording apparatus, the combination of a sound record, a. pickup cooperable therewith, means for relatively moving said record and pickup at a constant speed, means for superimposing upon said constant speed motion an oscillatory motion, a vibratory motor for supplying said oscillatory motion, a source of light, a photoelectric cell, an adjustable speed light interruptor between said source and said cell and operable to interrupt the passage of light therebetween at a vibrato periodicity, a manually operable variable opening shutter between said source and said cell, means to amplify the electrical impulses produced in said cell, and means for transmitting the amplified impulses to said vibratory motor to energize the latter.

5. Ina sound recording apparatus, the combination of an acousti-electric translating means, an amplifier for the electrical signals produced thereby, a sound recording means connected to said amplified, a record blank to-be operated upon by saidrecording means, means for relatively moving said recording means and record blank at a constant speed, and means for imparting' to said recording means andrecord blank an additional component of relative motion comprising alternate acceleration and retardation at a periodicity in the order of 7 C. P. S.

6. In an apparatus of the class described, the combination of a strip illm having a sound track thereon, means for moving said film at a constant speed, a photoelectric system for scanning the sound track on said iilm and translating the variations thereof into an electrical signal, means for vibrating the scanning portion of said system in a direction generally parallel to the direction of movement of said film, said vibrating means operating at a controllable frequency in the order of 7 C. P. S., and means for amplifying and utilizing the electrical signal produced by said photoelectric system.

7. ln an apparatus of the class described, a

iirst means to receive an eradicable record of sound, means for moving said first means at a constant speed, means to impress a record of sound upon said first means, a device to pick up said sound record and translate said record into an electrical signal, a vibratory motor operating at a. frequency in the order of 'l C. P. S. connected to vibrate said device along the path of movenient of said first means, means for amplifying and utilizing the electrical signal produced by said device, and means for eradicating the sound record from said first means after it has moved past said device.

d. The method of improving polyphonic music which comprises translating the musical sounds into two channels of electrical impulses, moduletting the electrical impulses flowing through one of the channels at a vibrato periodicity and to a vibrato extent, mixing the electrical impulses of the two channels, and making a record of the combined electrical impulses. Y

e.' .in an apparatus of the class described, the

vcombln.ation of a plurality of identical sound records, a pickup for each of said records, means for moving said records in synchronism, means for moving one of said pickups with respect to its record at a vibrato periodicity, a frequency responsive filter connected.- to atleast one of said pickups materially to attenuate certain frequencies in the signal derived from its pickup, ,means for selectively mixing the signals from said pickups, and means for amplifying and utilizing the resulting combined signal.

10. In apparatus of the class described, the combination of a phonograph turntable and pickup, motor means for driving said turntable, a resilient mechanical drive coupling between said motor means and said turntable, the compliance of said coupling being so related to. the rotary moment of inertia of said turntable and parts moving therewith that said turntable will have a natural frequency of oscillation, in the order of 7 C. P. S. with respect to said motor means, and means for causing said motor means to be accelerated and retarded cyclically at a frequency in the order of 'I C. P. S.

. 11. The combination set forth in claim 10, in which said motor means comprises a synchronous motor, and in which the means for causing the motor means to be accelerated and retarded cycli cally comprises a varying frequency source of electrical energy for said synchronous motor. n

12. In an apparatus of the class described. the combination of a phonograph turntable and pickup, motor means for driving said turntable, a resilient driving connection between said motor means and said turntable, and means for intermittently applying a braking torque to said turn table at a periodicity in the order of 7 C. P. S.

13. The combination set forth in claim 12, in which said braking torque applying means comprises a mechanical brake cooperable with said turntable to retard the latter, and means driven by said motor means'for operating said brake.

y14. The method of improving a musical tone lacking vibrato which comprises modulating the tone frequency bymeans of a frequency in the order of 6 C. P. S. which is modulated by a frequency in the order of 1.5 C. P. S.

15. The method improving musical tones which comprises modulating the tones by a, frequency varying cyclically between frequencies of the orders of 5.5 and 6.5 C. P. S. at a periodicity of theorder of 1 C. P. S.

16. In a sound apparatus, a phonograph record, a turntable therefor, a motor for rotating said turntable, a resilient driving connection between said motor and turntable, the compliance of said spring connection being related to the rotary moment of inertia of said turntable and parte rotating therewith that said turntable will have a natural frequency of oscillation in the order of 'l C. P. S., and means for varying the eective driving torque of said motor at approximately said natural frequency of oscillation.

1'?. n apparatus of the class described, the combination of a phonograph record, means for rotating said record at a constant speed, a pickup cooperable with said record, a resilient support for said pickup, a iiexible tape having one end thereof connected to said pickup, and e. panel forming an anchorage for the other end of said tape, said tape and panel diverging at an acute angle, whereby intermittent manual pressure on said tape will cause corresponding oscillation of said pickup and result in frequency modulation or the signal produced by said pickup.

lS. ln apparatus of the class described, the combination of a sound record, means for moving said record at a constant speed, a pickup cooperable `with said record, a resilient support for said pickup, a, exible member having one end secured to said pickup, and a :dried anchorage for the other end of said flexible member, whereby intermittent manual pressure on said member will cause correspon oscillation of said pickup and result in frequency modulation of the signal produced by said pickup. r

'19. In an apparatus of the class described, the combination of a sound record receiving member, means for moving said member at a constant speed, a plurality of microphones, recording means cooperating with said member and receivingI signals from said microphones, respectively, for impressing separate sound records upon said member, a pair of pickup devices spaced from said recording means in the direction of movement of said member, manually controllable means for oscillating one of said pickup devices in the directionof movement of said member at a frequency in the order of 6 C. P. S., an adjustable mixer for combining the signals produced by 'said pickup devices', and means for utilizing the mixed signal.

20. The combination set forth in claim 19 in which said member comprises an endless telegraphone tape, in which said recording means comprises electromagnetic means for elementally magnetizing said tape and in which said pickups are responsive to the elemental magnetization of said tape. A

2l.. The combination set forth in claim 19 in which the means for utilizing the combined signal ,from said mixer comprises a phonographic v recording apparatus.

22. The combination set forth in claim 19 in which the means for oscillating said pickup comtering mesh.

24. In an apparatus for introducing a vibrato effect into an original musical signal, the combination of meansfor producing a temporary moving wave pattern representing the original signal, a device for picking up the wave pattern from said means, and means in eiect causing oscillatory relative motion between said pickup device and said moving wave pattern producing means ata rate in the order of 6 C.`P. S., whereby the signal picked up by said device will be the original signal phase modulated at the oscillating frel quency.

25. In an. apparatus for introducing a vibrato effect into an original musical signal, the combination of means for producing a temporary moving wave pattern representing the original signal, a device for picking up the wave pattern from said means, means causing oscillatory relative motion between said pickup device and said moving wave pattern producing means comprising a motor, and means electrically generating random oscillations whose average frequencies are in the order of 6 C. P. S., said last named means being connected to said motor to cause the latter to execute corresponding oscillations, whereby the signal picked up by said device will be the d trical signal, a magnetizable record, means for magnetically recording said signal on said magnetizable record, a magnetic pickup cooperable with said record, an output-system including an amplier and electro-acoustic translating means i coupled to said pickup, means for moving said record with respect to said' recording means and said pickup in a direction such that the record passes the recording means and then the pickup, and means for imposing additional relative oscillatory movement of said ,pickup and said record,

said latter relative movement being of a frequency in theorder of 7 C. P. S. and of amplitude sumcient to impart a pleasing vibrato eect to the music produced lating means.

27. In an apparatus for introducing a vibrato eiect into music which is in the form of an electrical signal, a magnetizable record, means for by said electro-acoustic transmagnetically recording said signal on said mag-v netizable record, a magnetic pickup cooperable with said record, means for moving said record with respect to said recording means and said pickup in a direction such that the record passes the recording means and then the pickup, and

means for imposing additional relative oscillatory movement of said' pickup and saidrecord, said latter relative movement being of a frequency in the order of 7 C. P. S. and of amplitude suflicient to impart a pleasing vibrato eiect tothe music.

`28. In an apparatus'for introducing a vibrato eifect into music which is in the form of an electrical signal, a magnetizable record, means for magnetically recording said signal on said mag- 40 netizable record, magnetic pickup means cooperable with said record, means for relatively moving said record and one of said means at a constant speed, means for relatively moving said record and the other of said means at said cony stant speed with an additional superimposed oscillatory motion of a frequency in the order of 7 C. P. S. and of an amplitude sufcient to introduce a musical vibrato in the musical signal appearing in said pickup, and a signal utilization means coupled to said pickup.

29. An apparatus for producing music having a vibrato, the combination of a polyphonic instrumentality the output of which comprises an electrical signal which may include a large number of diierent frequencies many of which are not harmonically related, a unitary vibrato means coupled to said instrumentality for introducing a vibrato effect in the frequencies contained in the output signal thereof, said unitary vibrato means comprising time-delay means, an electrical pickup coupled to said time-delay means, and means for periodically varying the length of the time-delay produced by said time-delay means at a vibrato periodicity in the order of 7 C, P. S., the extent of the variation in time delay being suiicient to produce frequency changes between 0.1% to 3.0% above and 0.1% to 3.0% below the frequencies present in the output signal of the polyphonic instrumentality, and signal utilization means coupled to said pickup.

JOHN M. HANERT.

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