US2039659A

US2039659A - Electrical musical instrument

Info

Publication number: US2039659A
Application number: US727941A
Authority: US
Inventors: Ranger Richard Howland
Original assignee: Individual
Current assignee: Individual
Priority date: 1934-05-28
Filing date: 1934-05-28
Publication date: 1936-05-05
Anticipated expiration: 1953-05-05

Description

R. H. RANGER ELECTRICAL MUSICAL INSTRUMENT May 5, 1936.

Filed May 28, 1934 4 Sheets-Shut 1 INVENTOR R. H. RANGER BY Wf ATTORNEYS y 1935- v R. H. RANGER 2,039,659

ELECTRICAL MUSICAL INSTRUMENT Filed May 28; 1934 4 Sheets-Sheet 2 I i6.J

INVENTOR ATTORNEYS 4 Sheets-Sheet 3 Elf:

R. H. RANGE 1R ELECTRICAL MUSICAL INSTRUMENT Filed May 28, 1934 66 67 f U lll May 5, 1936.

INVENTOR R. H. RANGER B v M ATTORNEYS I 1&0 15-3 y 936. R. H. RANGER 2,039,659

ELECTRICAL MUSICAL INSTRUMENT Fi-led May 28, 1934 4 Sheets-Sheet 4 m 143 m5 m5 1 153 1 134 155 1 L156 LL13? 95? 4 ,96 'Q I I INVENTOR. R- H. RANGER A TTORNIEYS.

Patented May 5, 1936 srrss 17 Claims.

This invention relates to electrical musical systerms of the type in which musical tones are produced by means of electrical oscillations.

It is an object of the invention to provide an improved instrument of this type. Sound production in musical instruments by means of electrical oscillations is an old expedient and usually has involved the drawbacks of high cost, prohibitive space requirements, mechanical or electrical instability, high maintenance cost, high noise level, and musical results which did not warrant many proposed electrical systems. 'This invention provides an instrument with none of these drawbacks.

The present invention concerns a musical instrument involving the use of photo-electric or other light sensitive cells whose electrical output is influenced through the use of an interrupted light beam. In the past instruments have been devised in which rotating apertured discs interrupted a light beam with a frequency corresponding to the pitch of the desired musical tone. One serious drawback to such a system was that unless the openings were alined with extreme'accuracy disagreeable variations in frequency, intensity, or both resulted from even minute eccentricities in the mechanical construction. Another problem was to maintain the speed of the apertured discs absolutely constant.

One object of the present invention is to provide an electrical musical instrument in which these difficulties are overcome. To this end I employ a vibrating element of. reliable frequency as a control element for the variable intensity of the light. As an illustrative. device an air driven reed oi the type commonly employed in reed organs will be described. The invention, however,

is not limited to the use of an air-driven reed interrupter. Other vibrating devices may be used for light interrupters such as electrically maintained reeds, strings, plates, or membranes. I

prefer the use of organ reeds as their cost is very low and their operation reliable.

Another object .of my invention is to provide an electrical musical instrument whose space requirements are low. In the instrument to be disclosed only 72 vibrating reeds are needed to produce the desired notes in -.a large number of tone colors through the musical pitch range.- Many times this number of ordinary reeds or pipes would be required to produce a corresponding numberoi notes and tone colors in a pipe organ with a consequently larger space requirement.

Still another object is to provide an instru- (Ci. fi l-J) ment whose action shall be as nearly instantaneous as possible and permit no delay which the ear is capable of detecting. I provide a keyboard which conveniently may be like that of a modern pipe organ console. Depression of a key closes an electrical circuit which causes a lamp to be come incandescent the emitted light of which is interrupted or given a varying intensity by the vibrating reed and then falls upon the sensitive surface of a photo-electric cell which converts the light oscillations into electrical oscillations with subsequent electrical amplifiers and assc ciated sound projectors. A suificiently high volt age is applied to the filaments oi the lamps so that they become fully incandescent immediate ly upon closing of their circuits by depression oi the keys of the instrument. This gives an ac= tion tothe instrument far superior to that of the pipe organ; that is the length of time between depression of the key and. perception oi the corresponding acoustical phenomena is impercepti= tale in the case of my instrument, whereas this time interval for a pipe organ, esmcially for the long pipes whose air columns take time to be set into vibration, is considerable.

Another object is to provide a musical instru-= ment whose tone color may be altered conven iently and through a wide range.

Still another object is to provide a musical in strument whose overall dynamic range may be. varied over a very wide range irrespective of tone color. For instance. the dynamic level of a flute tone color may be varied from the threshold oi audibility to any level above this by suitable. control of the electrical output of the amplifier.

The invention in a preferred form provides for the electrical production of music through aplurality of elements each of which consists of the combination of a keyed light beam whose shape may be varied within predetermined limits, an

air-driven reed whose mirror surface periodically deflects the shaped light beam, a suitably positioned light slit upon which the shaped light beam is focused, a photo-electric cell whose sensitive surface is activated by the light passing through the slit, a suitable amplifier to' strengthen the photo-celloutput, and sound projecting equipment to convert the electrical energy delivered by the amplifier'into corresponding acoustical energy.

Such an embodiment of the invention will be described, but while this embodiment illustrates a preferred form it will nevertheless be understood that this description is merely illustrative members,

Fig. 4 is a view showing the light gate,

Fig. 5 is a view showing an alternative arrangement of elements of a unit for producing one note,

Fig. 6 is a detail view of the operating mechanism for adjusting the valve members of the light valve shown in Fig. 2,

Fig. '7 is a view showing a plurality of note units actuating one photo-electric cell,

Fig. 8 is a detail view showing an alternative form of light valve wherein a film of graded densities is substituted for the rotatable valve members of the light valve shown in Fig. 2,

Fig. 9 is a detail sectional view taken on the line 9-9 of Fig. 8,

Fig. 10 is an electrical diagram showing the amplifiers between a series of photo-cells and a loud speaker,

Fig. 11 is an electrical diagram of a device for use in producing a percussion type of note,

Fig. 12 is an electrical diagram of anamplifier blocking arrangement,

Fig. 13 is a diagrammatic perspective view showing two reeds positioned side by side within the same wind chest,

Fig. 14 is a diagrammatic view illustrating a manner of using one reed for producing the same note for two different manuals,

Fig. 15 is a diagrammatic view illustrating an arrangement wherein a shutter is provided for keying the notes,

Fig. 16 is an electrical diagram showing an arrangement whereby the content of each note is obtained from different reeds vibrating in harmonic relation.

In the musical instrument to be described for the purposes of illustration, the arrangements for the several notes are similar. The description of one set will suiiiciently illustrate the in vention. Each note is produced by light impinging upon a light sensitive cell, the light being varied in accordance with frequencies corresponding to the frequencies of the fundamental and overtones of the note to be produced.

The instrument is controlled from a console as usual and various stops are provided for modifying the quality of the notes. Referring to Fig 1 illustrating light control devices for two notes, lamps 5 are controlled by keys 8 at the console. The light from each lamp is directed along a suitable path to the light sensitive cell which conveniently may be a photo-electric cell 1. Devices are interposed in the path of the light between the lamp and the cell to cause a variation of the intensity of the light in accordance with the pattern of the fundamental and the desired overtones of the note to be produced. In the arrangement illustrated, the light from each lamp 5 passes through a condenser 8, a light valve 9, an optical wedge or variable density film III, focusing lens II and is reflected by the mirror surface l2 of the reed H from whence it passes through light gate l5 to the cell 1. The reed I3 is maintained in a state of continuous vibration at the natural frequency of the reed during operation of the instrument by means of a suction pump l6 which maintains suction in a chamber H extending beneath the row of similar units, each unit being connected to the chamber ll as by passages i8 and IS. The vibration of the reed serves to sweep the light beam across the light gate l5 and therefore by giving a suitable pattern to the light beam, the intensity of light incident upon the photo-electric cell 1 will vary in accordance with the desired pattern. To accomplish this result the lens II is adjusted to position to focus the pattern of the light valve 9 in the plane of the light gate 15. The light valve as best shown in Fig. 2 is formed to provide three rectangular ports 20, 2|, 22 controlled by rotatably mounted

valve members

23, 24, 25. The physical dimensions of the valve members will be determined by the amplitude of the reed vibration and the magnification of the optical system. In the original construction of the instrument the dimensions of the respective valve members and of the valve ports will be fitted to provide for the desired intensities of the light passing therethrough. These valve members are shown as nearly rectangular in cross-section and so shaped that when inthe position shown in Fig. 2 they permit passage of .the maximum amount of light but as they are rotated from this position they close the ports more and more until when turned at right angles to this position they entirely close the respective ports. suitably rounded at the corners so that the profiles will be of a proper shape to pass light of a good wave pattern as they turn. The particular shape of these valve members will be readily understood from the perspective view of the member 25 shown in Fig. 3.

Instead of a valve arrangement such as above described a type of valve may be provided in which the light pattern, that is to say the variation of intensity of the light passed through the valve opening will be controlled by variable density films. A suitable arrangement is illustrated in Figs. 8 and 9, wherein a variable density film is provided, the density of the sections 20, 2|, 22' of the film from top to bottom varying in accordance with suitable wave patterns. The amount of light passed through the three sections may be varied by the opening and closing of shutters 25 which are shown as pivoted and rotatable to pass more or less light. The intensity of the respective partials of the note to be produced is therefore controlled by the movement of these shutters.

The central valve member 24 of Fig. 2 is shown as of uniform taper throughout its effective portion. During vibration of the reed, which movement is naturally of sine character, the different portions of the valve member 24 will successively control the amount of light passing through the gate IS in such a manner that the variation in intensity at the photo-electric cell 1 will be in accordance with the sine wave pattern and will correspond to the fundamental frequency of the vibrating reed l3.

The valve member 25 is arranged to admit light to the photo-electric cell varying in intensity in accordance with a sine wave pattern, but at a rate corresponding to the octave of the fundamental, that is the second partial of the note to be produced. The particular shape of this valve memher is readily plotted by bearing in mind the natural sine wave movement'of the reed l3 and so designing the valve member that maximum light will be passed through the valve gate l5 twice during each complete oscillation of the reed The valve members are l3 and the variation in intensity will follow the sine wave pattern.

} The valve member 23 is designed to cause a suitable pattern of the light for the third partial of the note. The contour of this valve member may be readily drawn following the same principractice.

then only the fundamental and therefore the corple as in designing the valve member 25 but the shape should be such as to permit maximum light to be passed through the light gate l5 three times during each complete oscillation of the reed. As shown, this valve member is formed with a narrow section 21, above its center, but so positioned that during oscillation of the reed the larger portion 28 of the valve member will shut off the light from passing through the light gate l5 between two successive impulses of light as controlled by the section 21. The narrow portion 29 at the other end ofthe valve member permits a maximum of light while the reed is at one extreme of its oscillating movement. There are, therefore, three impulses of light impinging upon the photoelectric cell 1 during each complete oscillation of the reed. It will be understood that ordinarily, but not always, it is desirable that the fundamental of the note to be produced should be louder than the overtones and that the second partial should be about equal to the third. As a convenient arrangement for providing the desired relative intensities while retaining the possibility of further control by adjustment of the separate members of the light valve 9, the light gate H3 is so formed, as shown in Fig. 4, that the apertures 30, 3|, 32 through which the light from the ports, respectively 20, 23, 22 passes are of widths proportional to the desired intensities of the respec tlve partials. In order to make provision for voicing the instrument, the widths of these apertures may be made adjustable, if desired, as by providing

slides

33, 34, 35 movable to partially close the respective apertures. By this means the relative intensities of the several partials for the fully open position of the light valve 9 can be adjusted as desired. While provision for further controllingthe apertures from the console could be provided this is not ordinarily desirable.

In the operation of the instrument it is desirable that stops controlling the tone colors may be provided at the console in accordance with usual If, for example, a flute note is desired responding light admitted through the port 2| will be required. In order to provide such an arrangement whereby the valve members controlling the harmonic content of the note and controlling the respective overtones maybe operated for all notes of the instrument on the one console stop, the corresponding valve members are mechanically connected to be operated in unison. The valve members which control the fundamentals and those controlling the second and third partials are connected to three corresponding mem- Figs. 8 and 9 obviously can be similarly conbers for operation from theconsole. An illustrative arrangement isshown in Fig. 6. As here indicated each valve member 2| controlling the fundamental is connected by an operating arm 36 to an operating rod 31. Similarly the valve members 23 are connected by arms 38 to operating rod 39 and valve members 25 are connected by arms 4|] to operating rod 4|. In this way when the corresponding stop is drawn at the console all of the valve members controlling the particular harmonic are operated in unison. The light controlling shutters 25' of the arrangement shown in nected.

Console stops similar to the spot tablets or knobs of modern pipe organs may be arranged to ranged to control separately different sections so that, for example, the notes of the low keys can be given a flute quality while the notes of the higher keys are given a different quality.

Any suitable mechanism may be employed for actuating the operating rods. In Fig. 6 an electrical device is illustrated wherein an electric rotor such as a Selden motor or the like is gearconnected to each of the operating

rods

31, 39 and 4| to control the same. When the instrument is in operation the rotor element is energized to positively control the position of each control rod. As shown, the rotor has six poles any pair of which may be energized to bring the armature to the corresponding position. For example, when the opposite poles 45 and 46 are energized the rotor 41 will be drawn to the position indicated in Fig. 6. If it is desirable to move the rotor to an intermediate position between two pairs of poles two adjacent pairs of poles may be both energized to cause the rotor to be moved to and held in an intermediate position. This expedient may be carried further to the extent of magnetizing one set of poles with a greater magnetomotive force than the other.

In the arrangement illustrated in Fig. 1 and above described provision is made for controlling only the fundamental, the second and the third partials. In a larger instrument it is preferable to provide for control of the fourth, fifth and even higher harmonics as well as those already mentioned. For such purpose there are certain advantages in the arrangement illustrated in Fig. 5 in which two reeds are employed for each note. As shown, two

reeds

50, 5| are provided and suction is maintained in the chamber 52 in which these reeds are mounted. Upon depressing of the console key 53, controlling the particular note, both gas filled lamps 54, 55 are illuminated, condensers, light valves, lenses, the mirror surfaced reeds and light gates being provided to control the light beam passing to the photo-electric cell 56 as in the arrangement shown in Fig. 1. The light beams are periodically swept across the apertures of the light gates by the mirror surfaces of the vibrating

reeds

50, 5|. Through this method of using more than one reed or each note. the crowding of the controlling valve members and simplification of the mechanism can be obtained. Furthermore, the use of optical wedges, mirrors and other optical devices for bending light from the sides of the light valve can be avoided.

It is important that the

reeds

50 and 5| should vibrate at exactly the same frequency or at harmonic frequencies in order that all harmonics produced should be exact multiples of the fundamental. The advantages of reeds vibrating at the same frequency probably equal the advantages, of using reeds of two harmonic frequencies and that arrangement is adopted herein. If the reeds do not vibrate exactly in harmonic relation there will be a. beating effect between the harmonics which will be more or less unsatisfactory musically. To this end it is preferable to so arrange one mod on the wind chest 52 that it will be it shall be caused to vibrate at its own natural period. This can be accomplished, for example, by bending the reed slightly into the wind chamber or by other expedients. The natural frequency of the driven reed then enters only as affecting theamplitude of vibration which will be greater as the natural frequency approaches that of the driving reed. By making use of this resonance phenomenon the driven reed may be caused to vibrate at nearly as great an amplitude as the driving reed.

It will be noted that in the arrangements of Figs. 1 and 5 the photo-electric cells are each activated by light from two lamps. These cells operate satisfactorily if the light from other lamps is also superimposed for which reason it is possible to so arrange the apparatus that each photoelectric cell serves for several notes and the total number of cells is correspondingly reduced. An arrangement is indicated in Fig. 7 which makes this possible wherein the three units 60, G I, 62 are positioned at such angles that the light from all impinges upon the cells 63 and 64. It will be noted that the feature shown in Fig. 13 for application to a multiple manual instrument is incorporated in this arrangement,

. Amplfficatiou .--Any suitable amplifying arrangement may be used. In Fig. 10 is indicated an illustrative circuit. The number of photoelectric cells employed will depend upon the de sign of the instrument but the three shown will sufficiently illustrate the amplifying circuit. One pick-up amplifier may be associated with each cell or as many as twenty cells may be electrically connected in parallel or otherwise associated to feed into a single pick-up amplifier. It is also to be understood various mirror reflecting schemes may be employed to reduce the number of photo-cells required by reflecting a large number of light beams into one or more cells of suitable size. Referring to Fig. 10 each photo-electric cell 1 of the series is associated with a vacuum tube amplifier 65 of conventional design and each amplifler is provided with a suitable gain control 66. The outputs of amplifiers 65 are fed into transformers 61 whose secondaries are connected to tube matching resistances 6B. These resistances are connected in series and connected to the primary of transformer 69 whose secondary is'conoperate loudspeaker 15 at a suitable musical sound level. It will be understood by those skilled in the radio and broadcasting arts that amplifiers 65 and the connections to the transformer 69 constitute merely an illustrative arrangement for' feeding the several currents into amplifier 10. 'In eneral, the acoustic conditions andsize of audience will determine the size of the amplifier l0 and acoustic translating equipment 15.

It has been found that there are certain advantages in providing a plurality of separate amplifying and loud speaker systems for the different sections of the organ. The base notes of the pedal section especially in the case of an in strument to be used in a large auditorium should he placed on one separate system and the output controlled by each manual may advantageously be on a separate system. It is desirable to have separate amplification controls for each system.

Trem0lo.-In order to secure certain desirable forced to vibrate by the alternating pneumatic fluctuations in the wind chest rather than that musical effects it is preferable to provide a tremolo device. Perhaps the simplest way to do this is to provide a tremolo in the wind supply of the beater type long familiar to pipe-organ practice. Such a device is indicated at 76 in Fig. 1. Other electrical methods are possible, such as varying the exciter lamp voltages at the rate desired for the tremolo to be produced. A variable resistance 1'! controlled by a crank '18 is indicated in the light circuits of Fig. l to illustrate this arrangement. Alternatively a moving light shutter 79 Fig. 15 may be used periodically to change the illumination to give an intensity tremolo. The above mentioned beater tremolo will cause a small frequency tremolo in addition to the intensity tremolo.

Percussion tone.-Another important musical effect is that of the percussion tone. There are several methods of producing this effect. The

method preferred for the instrument illustrated I consists in providing a time delay relay associated with each note as indicated in the electrical diagram Fig. 11. When the console key 80 is depressed lamp BI is illuminated through the circuit shown by the current from the source 82.

Normally the switch 83 is closedcausing series resistance 84 to be short circuited. Immediately after the console key is depressed therefore the lamp 8t attains maximum illumination. Shortly thereafter (the time interval depending upon the 1 design of the time relay 85), the time delay relay opens the switch 83 and the resistance 84 is introduced into the lamp circuit. The voltage therefore is decreased because of the added series resistance 84. This change in illumination causes different period of delay.

The percussion tone may be obtained by other devices which reduce the intensity of the note after it is initiated as, for example, by providing a slow acting shutter in the light beam. Such a shutter is indicated at B6 in Fig. 5 and can be made to operate slowly by associating it with the armature of a slow acting electrical or pneumatic relay 81. bodiment of the invention affects only the light initiating the fundamental or the fundamental and part of the overtones giving a desirable effect.

Volume control-Volume control, which is of great importance musically, may be obtained in a number of ways. The method or methods which will give the most satisfactory results will depend upon the size and arrangement of the particular instrument under consideration. For

the one manual instrument, the output of the power amplifier may be varied by a control H associated with a console foot pedal 12 similar to the swell shutters foot control on a pipe organ console. Alternatively or additionally, a console pedal controlled resistance 93 (Fig. 1) may be introduced in series with the exciting lamps, the latter always being in parallel with each other. This method has several disadvantages and some special advantages. The one serious disadvantags is that the lamps have an undesirably long of such a series resistance is that the series re- This shutter when applied in this emsistance has a variable voltage drop across it depending upon the number of lamps that are excited. This results in causing the introduction of additional lamps to affect the illumination of the other lamps already excited. To illustrate, if

two console keys are depressed andthen a third is depressed, the addition of this third note would cause the other two'notes to become weakened.

This would give a new musical effect which, how-;

ever interesting for special purposes, is not suited for a general volume control. This disadvantage so'far as a'true volume control is concerned may beovercome bymaintaining all the excited lamps in a continuously illuminated state with said variable' series resistance associated. therewith and .keying the light beams by means ofquick-acting have at least one complete set of reeds associated with each manual. For certain celeste and en'- semble effects I prefer to use more'than one set of reeds per manual. See Fig. 5 and the description thereof. n the other hand, one set of reeds may be used for more than one manual by associating more than one light source with each reed. Such an arrangement is indicated in Fig. 14,

wherein light from two lamps '92 is reflected by the mirror'surface of reed 93 to cells 94.

For the two manual instrument, I may have tworeeds associated with the same musical pitch mounted in the same wind channel, for example as shown at-95 in Fig. 13. When so mounted, the two reeds may be made to vibrate at exactly the same frequency. It will be apparent that two sets of photo-cells 90 may be arranged to pick up the light beams associated with the respective manuals. A general volume control can be chtained by the manipulation of the final amplifier output as in the case of the one manual instrument. It is also desirable to have individual dynamic control over the output for each manual. For this purpose the two series of similar photoelectric cells will deliver their output through separately controllable amplifying devlces wherei by the relative intensity of the outputs of the two manuals can-be controlled independently applying the principles embodied-in the arrangement illustrated in Fig. 10. Obviously the .quality of the output initiated by the different manuals can also be controlled independently bysuitable adjustment of the light valves of the respective light sources. The particular arrangement of loud speaker shown is illustrative and not intended as excluding the use of other arrangements.

It will be noted furthermore that the arrange-- ments indicatedin Fig. 13 and Fig. 14 are adapted to be applied in combination with the arrangement of light sources, reeds and photo-electric cells indicated in Fig. 1 or 5.

Another method forobtaining control over the output of the two manuals is to have all the exciter lamps continuously illuminated and keying accomplished through the aid bf quick-acting shutters while a. series resistance under control of a. foot pedal is associated with the lamp for each manual. Such an arrangement is] indi-. cated in Fig. 15 wherein a shutter 91 keys the note and resistance 00 controls the intensity.

An alternative method for obtaining individ ual manual dynamic -control, which has some advantages, involves the use of devices operated so as to diminish the light available for exciting the photo-cell. To this end, I may provide an optical wedge or a film of varying density associated with each note, and connect all the optical wedges or films for a single manual to one operating rod; This rod may be moved in any suitable-way. These optical wedges or films can be situated at any point along the optical system. I prefer to situate them between the harmonic controlling light valves and the mirror surfaced reeds as indicated at I0 in Fig. 1. The voltages applied to the exciter lamps is always substantially the same and keying is accomplished by flashing the exciter lamps.

It will be noted that the light passing the light gate may be considered as one beam having a complex pattern or as three separate beams.

Amplifier bZocking..In order to avoid a noticeable photo-cell hiss and other stray noises in the output of the instrument it is desirable to provide a means for automaticblocking of the amplifier when no signal is applied. When no console keys are depressed, the instrument should be as quiet as possible. Unless some blocking arrangement is provided, the inherent photo-cell hiss and other stray pickup will be unpleasantly discernible during the silent portions of a musical rendition. When a note is being played the photo-cell hiss, etc. will be largely masked. During such times the blocking of the amplifier will be removed and it will the case of any amplifier. The grid of tube IN is biased to its normal value with battery I02. It will be seen that in series with this grid bat- ,tery to ground is a variable resistor I03. When a direct current flows through this resistance, there will be a direct voltage drop across it. This voltage will be added in proper algebraic sense to that of the normal bias battery I02. The operation of the circuit is such, that when no signal is applied, a current will be flowing through resistance I03 and thus the extra bias to the grid is adjusted by making resistance I03 the proper value, and it is of such a value that the grid of tube IOI becomes biased to cut-off when a current fiows through said resistance. Under such circumstances, tube IOI becomes inoperative and effectively blocks inherent photo-electric cell hiss and other stray pick-up. It will be seen that the secondary of transformer I00 feeds also to the grid of tube I05 through blocking condenser I00 and adjustable resistance H3 which condenser is introduced to block any direct current from affecting the potential ofthe grid of tube I05. Tube I05 is biased normally with battery I01 through resistance 3 and its operation is always that of a simple amplifier. The output of tube I05 is fed into transformer I08 which is supplied with a center-tapped secondary. This secondary feeds as a full-wave rectifier into two of the plates of tube I09 which is, inefl'ect, a combination of two diode and one triode elements. Parallel elements H0 and III constitute a load on this full-wave rectifier. When the primary of transformer I08 is energized, there will be a voltage induced in the sec-- qondary, and the grid of ti'ibe I09 will be at a negative potential due to the full-wave rectifier acsystem to become operative.

tion. This means that electrons emitted from the cathode of tube I09 will be blocked by the negatively charged grid of tube I09. The result is that the plate current will be zero and consequently no voltage drop will appear across resistance I03. This leaves the bias on tube IOI at its normal value, and said tube operates as i an amplifier delivering its output to transformer I04 whose secondary feeds to the power amplifier and loud speakers. This situation exists when a signal is applied. Grid potentiometer H3 is made adjustable in order that the inherent photo-cell hiss will not of itself cause the The minimum signal intensity as compared with the noise level will determine the position of slider M4 on potentiometer resistance II3. Considering now the case where no signal is applied, there will be no voltage across the secondary of transformer I08. Consequently, there will be no rectifying action of tube I09, and the center-tap of transformer I08 and the grid of tube I09 will be at zero potential. At zero grid potential, the electron flow from the cathode of tube I09 will not be impeded, and a cathode to plate electron current will flow. Battery H2 supplies the necessary positive plate potential for tube I09. Under these circumstances a current will flow through resistance I03, and a voltage drop will appear across said resistance. This extra voltage drop causes the grid bias of tube IOI to rise to cut-oil thus making the tube inoperative. Thus, no inherent noise, etc. pass tube IIlI when no signal is applied. The values of resistance H0 and capacitance III will determine the time delay in blocking tube I 0|. That is, the charge on condenser III will take a finite time to leak 01f through resistance H0. Also, as the grid of tube I09 is connected to said condenser its potential will drop in said finite time. The length of this period is determined by the value of capacitance III and resistance IIO. The presence of this time delay combination is made preferable because the circuit as a whole is not instantaneous in operation when a signal is applied-there is a slight delay. To overcome this difiiculty, I include this time delay element. Musically, this means that swift moving passages may beplayed without having tube I OI blocked between each note of said swift moving musical passages.

For very high notes the reeds are short and relatively difiicult to tune and pipes or reeds of the usual type commonly used in pipe organs are small requiring relatively little space. Accordingly, it is practicable to use for the'upper notes a unit having such pipes or reeds enclosed in a sound proof box. The output of these pipes or reeds may be picked up by a suitable microphone and superimposed upon the output of the photoelectric unit or it may be delivered to a separate loud speaker through a suitable amplitude control.

Obviously various modifications of the arrangements illustrated may be made such as providing other arrangements for keying as by means of setting the reeds in vibration individually as is common practice in ordinary reed or pipe organs. This would eliminate certain noises. Also the manner of controlling the light in response to the movement of the reeds may be varied as convenience may require. For example, it is possible to vary the amount of light as the reed vibrates by an arrangement wherein the light passes the end of the reed and the vibrating reeds act as a light valve opening and closing the light aperture.

The tuning of the reeds may be accomplished in various ways including filing as is common practice or by varying the air pressure as by valves II5, Fig. 1, or by other known expedients.

Instead of using merely one or two reeds to produce the whole content of each note, the arrangement may be such that each partial of the note is produced under control of a separate reed. To accomplish this an arrangement embodying certain principles of my prior Patent No. 1,901,985 may be adopted. Such an arrangement is illustrated in Fig. 16 wherein is shown a circuit providing that each note as produced may consist of a fundamental and three overtones. As herein illustrated the intensity of the overtones and fundamental may be varied relative to each other to provide the desired quality of the notes. In each case the overtones are obtained from the corresponding units of the higher (or lower) notes of the instrument.

In the diagram incandescent lamps I2I to I 21 may be those lamps associated with reeds of pitches corresponding to the C keys on the instrument or to the keys of notes harmonically related to each other. These keys and lamps are associated with key switches I3I to I31 respectively. Each key switch is a gang switch arranged to close the circuit of the lamp corresponding to the key and also the desired lamps corresponding to higher or lower C notes or other partials to give the desired harmonic content. cuit connections between each switch and the lamps are similar, each switch except at the ends of the series being shown as arrangedto close exciting circuit for a lamp corresponding to the fundamental of the note, a second lamp corresponding to a sub-harmonic and two lamps corresponding to upper harmonics. For example, switch I32 may close a circuit to lamp I22 and also to lamps I2l, I23 and I24. In the circuits for each key switches and resistances are introduced to provide complete control of the harmonic content from the console. Switches I40, which may be connected to form a gang switch controlled from the console, may be closed or opened to provide or omit the subharmonic coupling and variable resistances I4I may be adjusted, also by gang control, to determine the intensity. Switches I42 and variable resistances I43 similarly make possible the control of the fundamental and switches I44 and I46 with resistances I45 and I4! serve the same purpose for the upper harmonics.

It will be understood that if the instrument is tuned according to the even-tempered scale, it is impossible to select notes from said scale which wil be exact odd harmonics of a fundamental 01 a note of said even-tempered scale. However, they may be approximated quite closely with notes selected from the even-tempered scale and the odd harmonic pitches obtained in this way are suitable musically for many purposes.

I claim 1. A musical instrument comprising, in combination, a series of keys, light sensitive cells. a series of vibratory elements, means controlled by said keys and vibratory elements for causing light of an intensity varying under the influence of said vibratory elements to impinge upon said light sensitive cells and means for amplifying the output of said light sensitive cells.

2.. A musical instrument comprising, in combination, a light sensitive cell, a source of light The cirlight beam comprises a film-of density varyi" operable to cause light to impinge upon said cell, a vibratory element, means whereby the intensity of the light impinging upon said light sensitive cell is caused to vary under control of said vibratory element, means for converting the output of the light sensitive cell into sound and keying means operable to control the inception and termination of the sound.

3. In a musical instrument, in combination, a light sensitive electrical cell, an amplifier arranged to receive the output thereof, a light source arranged to direct a beam of light onto said light sensitive cell, and a vibratory reed in the path of light between the light source and the light sensitive cell for varying the light intensity at the cell in accordance with a pattern approximating a sine wave pattern of audio frequency.

4. In a musical instrument, in combination, a light sensitive electrical cell, an amplifier arranged to receive the output thereof, a light source arranged to direct a beam of light onto said light sensitive cell, and means in the path of light between the light source and the light sensitive cell for varying the light intensity at the cell to correspond to the harmonic composition of a note to be produced comprising a vibratory element and means cooperating therewith to cause a variation in intensity at a rate difiering from the rate of vibration by a predetermined factor.

5. In a musical instrument, in combination, a light sensitive electrical cell, an amplifier arranged to receive the output thereof, a light source arranged to direct a beam-of light onto said light sensitive cell, and means in the path of light between the light source and the light sensitive cell for varying the light intensity at the cell to correspond to the harmonic composition of a note to be produced comprising a plurality of vibratory elements and means cooperating therewith to cause a variation in intensity at rates controlled by the rates of vibration;

6. In a musical instrument, in combination, a light sensitive electrical cell, an amplifier arranged to receive the output thereof, a light source arranged to difect a beam of light onto said light sensitive cell, means in the path of light between the light source and the light sensitive cell for giving a pattern to the light beam, a vibratory element and a mirror actuated by the vibratory element and operative during oscillation to transmit to the light sensitive cell difierent portions of the light beam to thereby deliver to the cell light varying in intensity in accordance with the harmonic composition of a note to be produced.

'7. A musical instrument as defined in claim 6, wherein the means for giving a pattern to the light beam comprises a lightgate and devices adjustable therein for giving difierent patterns to the beam.

8. A musical instrument as defined in claim 6, wherein themeans for giving a pattern t"-';; i;the

in accordance with the patternto be given to the light beam and means for varying the amount of light is provided.

9. In a musical instrument, in combination, a

- light sensitive electrical cell and an amplifier arranged to receive the output thereof, means for directing a beam of light onto said cell, means for periodically varying the intensity of the light at said cell including a vibratory reed and means for maintaining said reed in a state of vibration,

' directing a beam of light onto said cell, means for periodically varying the intensity of the light at said cell including a reed and pneumatic means for vibrating said reed at its natural frequency, and keying means for controlling the illumination from said lamp.

\ 11. In a musical instrument, in combination, a light sensitive electrical cell and an amplifier arranged to receive the output thereof, means for directing a plurality of beams of light onto said cell and vibratory reeds for varying the intensities of said beams of light at frequencies corresponding to the frequencies of difierent par- -tials of a note to be produced.

12. In a musical instrument, in combination, a light sensitive electrical cell and an amplifier arranged to receive the output thereof, means for directing a plurality of beams of light onto said cell and vibratory reeds for varying the intensities of said beams of light at frequencies corresponding to the frequencies of different notes to and means cooperating with said reeds for varying the light intensities of respective beams of light to correspond to the frequencies of different partials of the note to be produced.

, 14. In a musical instrument, in combination, a series of light sensitive cells, a series of light sources arranged to direct beams of light to said cells, keying means for controlling the light sources individually at the will of the operator, a series of .vibratory reeds arranged in the paths of the beams of light operative to vary the light intensityas transmitted to the light sensitive cells to correspond to the patterns of the several notes to be produced.

15. Amusical instrument as defined in claim 3, wherein a variable resistance is interposed in the light circuit and means for varying the resistance in accordance with a predetermined pattern is provided.

16. A musical instrument comprising, in combination, a light sensitive cell, a source of light, means for forming a light beam, means for vibrating said light beam transversely, a light valve in the path of said light beam arranged to cause variation of the intensity of the beam as passed through the valve in accordance with the rate of vibration of the light beam.

17. A musical instrument comprising, in combination, a light sensitive cell, a source of light, means for forming a light beam, means for vibrating said light beam transversely, a light valve in the path of said' light beam, said light valve comprising sections extending transversely oi the light beam in the direction of its vibratory movement and varying in density substantially in RICHARD HOW RANGER.