US2142580A - Electrical musical instrument - Google Patents

Description

Jan. 3, 1939. v c. E. WILLIAMS 2,142,580

ELECTRICAL MUSGAL INSTRUMENT Filed March 6, 1933 4 Sheets-Sheet l gmc/1MM CHARLES E WlLLmms C. E. WILLIAMS ELECTRICAL MUSICAL INSTRUMENT Filed March 6, 1933 4 Shets-Sheet 2 CHARLES EWILLIAMS Jan. 3, 1939. C E wlLLlAMS 2,142,580

ELECTRICAL MUS IGAL INSTRUMENT FIG. 3

Jan. 3, 1939. c. E. WILLIAMS LECTRICAL MUSICAL INSTRUMENT Filed March 6, .1933 4 Sheets-Sheet 4 FIG FIC5-4- Firm FIGLS Bumm/vtm CH'ArzL'ES EWILLIAMS Y Mtv/MAL;

Patented Jan. 3, 1939 UNITED STATES ELECTRICAL PATENT OFFICE MUSICAL INSTRUMENT of Delaware :Application March 6, 1933, Serial No. 659,667

comms.

kThis invention in general relates to electrical musical instruments and in particular to means for incepting, generating,l controlling, modulating,

selecting, combining and coupling alternating electrical currents for the production of musical sounds when used with a suitable output system, the Alatter ordinarily including amplifying and loud speaking systems. An instrument con-A structed in accordance with this speciilcation may be'used in place of a pipe organ or as an orchestral instrument or it may be used for accompanying and solo purposes. Y

Incorporated in this instrument are meansv for regulating the number and amplitude of harmonies inthe musical tones.

`Another object is to provide for the operation of the instrument when desired, by more than one player.; at the same time by the use of a plurality of keyboards. These keyboards may be reproduced in whole or in part to suit the frequency range required for'the individual player.

Another object is to provide means for producing avibrato.

Another object is to provide means for-monitoring and remote control of various qualities in the music Vwhen produced in a concert hall with additional features such as indicators to show the re1- ative amplitudesof Asound Waves as received at a particular point in the concert hall as well as the settings and adjustments of the remote control devices.

In this invention alternating currents of audible frequency are produced by suitable generators and associated circuits. One generator is provided for each frequency desired and all are operated continuously and connected to an amplifying and output control system or systems by means of one or a plurality of keying systems. Musical sounds are produced in the speaker systems only when the keying systems are operated.

By operating the generators Vcontinuously better frequency regulation and stabilization can be obtained than can behad with generators which are keyed to produce intermittent operation.- Another advantage that can onlyv be' had with continuously operated generators is the availability of thev generated frequencies for use in combining with other harmonically related frequencies to produce various wave forms with resultant tonal effects. This results in a reduction in the number of tone generators required and. permits of a simplified arrangement.

This instrument is provided withv means whereby one or more players may play it simultaneously using the entire frequency range. of the instrument in whole or in part. For example, identical keyboards may be electrically connected to the Igenerating system and to the output amplifying system for operation by the different players, or, one keyboard group may be of a type similar to 5 the present day pipe organ manual while other groups may be of a type shown in the accompanying'illustrations and described in the following text.

This combination and arrangement permits of l a more simplified arrangement than has heretofore been obtainable by the use of individual generators for each tone vfrequency with associated generator groups to provide harmonic frequencies for combination with the fundamental. In my l arrangement the harmonic components desired for any given tone frequency are obtained by vintroducing the desired amount of harmonic energy into the keying and amplifying system, said harmonic energy being derived from other fundamental tone generators of the system.

Another advantage voi this system is that in the case where a plurality of keyboards are operated in connection with the master generator system the" pitch of the musical tones regardless of which keyboard or player is controlling the keying. In systems previously developed wherein a complete system of generators is provided for each keyboard or player difficulty` is frequently experienced vin synchronizing frequencies. 1

In systems employed in similar musical instruments up to the present time wherein a multiplicity of generators are connected to the output or amplifying devices difficulty is experienced in maintaining consistent volume or amplitude levels due to the fact that the output or load impedance varies with the number of units in parallel. In my arrangement this is overcome to such a degree that it cannot be detected by the ear, by means of combining high impedance generator output circuits to work into a succeeding shunt circuit of relatively low impedance.

Vibrato effects, better defined as frequency modulation, frequency and amplitude modulation in combination, or phase modulation, are at times desirable and necessary in the rendition of most compositions. Previous attempts to obtain this effect in electrical instruments of this generaltype have resulted'in the production of a tremolo or 50 amplitude modulation only. The latter, used extensively in pipe organs, is rnot as desirable to those skilled or trained in the art of music as is a vibrato eect.

Figure l is a schematic diagram of a typical will be identical 25 circuit arrangement with continuously operated tone frequency generators harmonically related frequencies with switching and keying devices for connecting the output to an amplifying and loud speaker system. Embodled in this arrangement are controls for both foot and hand adjustment of volume. i

Figure 2 shows an arrangement wherein tone frequencies are generated by means of electronic tube oscillators. 'I'his arrangement includes a system of output coupling and control devices, a harmonic intercoupling system and multiple keying connections.

Figure 3 shows in addition to the devices of Figures 1 and 2 a method of producing a vibrato effect, means for tuning and a system of remote monitoring controls for regulating output volume and tonal qualities with telltale indicating devices located in the vicinity of the players or conductor.

Figures l to 9 inclusive show alternative arrangements of contacts to permit keying of the instrument by contacting with the hands.

The nature and scope of this invention can best be understood by reference to the drawings. In Figure 1 are shown tone frequency generators, indicated by IU, fZIl, JS and i600 which generatealternating currents having frequencies of 100, 200, 300 and 400 respectively. Each of these is connected to an output coupling device consisting of variable impedances 8a, Bb andc. This particular coupling system is used in a manner-similar to that employed extensively in telephone and carrier frequency systems. The impedances may be adjusted to regulate the amplitude of the currents in either or both of the coupled circuits or the degree of coupling desired. This is of particular value in that large changes in output circuit impedance result in negligible effects in the generator circuit. Similar generators which are necessary in connection with the generators and system `shown are omitted from the drawings, for sake of simplicity, but connections thereto are indicated by f, fllt, JS, H200 and fito. ISa, Ib, IIc and ltd are contact devices complemental to the respective contact devices fI, f2, f3 and fli, which in this arrangement illustrated bear the relation of fundamental and second, third and fourth harmonics. The gaps between contacts I6a, Ib, Ic and Id and the respective contact devices of fl, f2, f3 and ffl are arranged and connected in such a manner as to permit electrical connection to be made with the hand or body, 1

or in any convenient manner, to complete the circuit across such gaps to terminal Il, allowing current to ow to the terminals of variable impedance IB. The player may or may not be in contact at all times with the conductor connecting to Il. The contact devices I6a, I6b, 16e and Id are shown in detail in various forms in Figures 4 to 8 inclusive. II is a variable impedance coupling device for regulating the degree of intercoupling of a harmonic frequency to the fundamental tone frequency. Said harmonic component is obtained by connection to another tone generator whose frequency is such as to bear the required harmonic relation to the fundamental. 1n all cases Where reference is made to harmonic frequencies it is the intention to consider as harmonic frequencies all notes of the tempered musical scale that correspond to the true note but which are modied or detuned a slight amount to permit the use of ther instrument in various musical keys. It is the intention that either the true harmonic frequency or the corresponding tempered frequency be considered herein as harmonic frequency. I0f2, IIJf3 and Illf are switches for the selection of second, third and fourth harmonics respectively; all switches bearing the same designation are operated simultaneously by means of contact keys or magnets similar to stop switching arrangements used in pipe organs. In actual operation, if the required tonal quality necessitates fundamental and harmonic amplitude relations, such as fundamental IIIIJ, second harmonic 25 and fourth harmonic Il); switches I0f2 and lfli are closed, impedances II will be adjusted to limit the associated harmonics to the proper value, thereby obtaining the desired tone color. Keying of the fundamental plus the second and fourth harmonics will beaccomplished by completing the circuit through the associated keying contact devices Ia or Ib, etc., means to that end being shown in Figures 4 to 9 inclusive. Inthe event only the fundamental tones are to be played all of the harmonic selector switches will remain open. The variable impedance I8, known herein as shunt load impedance, should be of value relatively low compared to that of the generator output coupling device. This will permit of the output circuits of a plurality of generators being connected in parallel, with the result that the volume of a given tone frequency will remain audibly the same regardless of the number of tones being played simultaneously. This variable impedance I8, also serves as a maximum volume limiter. It may be adjusted prior to a performance to limit the volume from the speaker system to that which will not overload the amplifying or speaker system attached thereto and which is consistent with the music to be played. Such adjustment should be made with all other volume controls set in a maximum position. A hand operated volume control located preferably near or upon the instrument keyboard is indicated by variable impedance I9 while 2D is a variable impedance for volume control with pedal or lever operating mechanism arranged by means of springs o r other similar devices to return to an off position when pressure is removed. By means of these devices the volume can be controlled within the limits imposed by the variable impedance I8. Any suitable output system may be employed, and in the drawings the same includes the audio frequency amplifier, 2|, and the band pass or suppression filter 22, while 23 is a speaker selector system, and ZII and 25 represent loud speakers. These devices are in themselves common in the electrical art and need no further description. Switch 3&1. and variable impedances 35a and 3th constitute a quick acting damper circuit connected in shunt with the output system for the purpose of cutting the volume off or on, to a, denitepredetermined value or to zero value and at a rate determined by the adjustment of the impedance elements. It is intended that it be attached to a pedal operated mechanismand operated by the player.

In Figure 2 a more detailed circuit arrangement may be found wherein a form of generator comprising an electronic tube I, inductances 2 and 3, condensers 4 and 'I are indicated. Inductance 3 and condenser Il comprise an oscillatory circuit. This oscillatory circuit in conjunction with the electronic tube and associated power source constitutes a means for incepting tonefrequency currents. Thisvgenerator is coupled to the output keying system by means-of coupling impedances la, 8b and 8c. These impedances are v arranged in such a manner that the magnitude oi' impedance included in the input circuit (side presented to the generator) Is low relative to the magnitude of impedance in the output circuit and are arranged to provide high attenuation between the input and output, thereby providing a substantially constant load on the generator and thereby preventing undesirable` transients from being produced and combined with the tonefrequency currents as a result of keying. These transient currents would otherwise produce the effect known as key thumps. 5 and 6 represent respectively plate and grid potential sources as used in common practice with similar vacuum tube circuits. Switches are operated by the player to produce frequency M00 in the speaker system, switches 9a are operated to produce i200 while switches 9b when operated produce frequency f300. All switches bearing thesame designation are operated simultaneously either by means of one key or by a relay operated by a key. Harmonic coupling devices II regulate the tone color or timber by regulating the amplitude of the harmonic components. Switches IN2 are operated simultaneously by means of contact keys or magnets similar to stops on the present day pipe organ. With these switches closed the second harmonic of the associated frequency will be present when keying switches are closed. Similarly when the third harmonic is desired switches I0f3 are closed and coupling to the desired generator is regulated by associated coupling device II. Provision is made for varying the degree of harmonic coupling by controlling the flux density in the magnetic material within the field of impedances IIa.- This is accomplished by controlling the current which energizes windings IIb; in case of the units for coupling of second harmonics the switch I2 and variable'resistance I3 is used, while switch I4 and variable resistance I5 are used similarly for the third harmonic control circuit. Contact devices I6a, IIb and I6c previously referred to are connected in parallel with switches 9, 9a and 9b in such a manner that the circuits are completed to the terminal I'I by either the switches or the keying contact devices.

Figures 4 to 9 inclusive show in detail some of the ways in which the keying contacts may be arranged. In Figure 4 the keys shown are similar in arrangement to that of the standard piano or organ keyboard. The keys however may be either fixed or movable, preferably they are of a conducting material so that by contacting with the hand the circuit will be completed to the contact rail to which is attached the other side of the circuit I'I. This rail or strip should also be of conducting material. By contacting it with the thumb and varying the pressure or area of contact the volume may be readily controlled as desired by the player. The form in which this principle may be applied may assume various designs for example that as shown in Figure 5 where the size and arrangement of keying contacts are different from that shown in Figure 4, the principle of operation remains the same. Figure 6 shows a further modification wherein both sides of the circuit are terminated on each key in alternate order but spaced forinsulating purposes. By making contact on any two or more strips the circuit is completed. All shaded areas are connected to the common point Il while all other areas designated by the same identification number are interconnected electrically to the other side of the circuit. Figure 'I shows another form in which these contact areas may be arranged. In Figure 8 the two sides of the circuit are terminated in small areas insulated from each other. All shaded portions are connected in common to the same side of the circuit, designated as Il. By placing the finger on the portion nearest the bottom of the illustration a lower contact resistance will result as the area of contact is greater than when the finger is placed at the upper part of the key where the contact area is much less. By touching the key at the proper place the desired volume will result. Figure 9 shows an arrangement where multiple contacts are arranged so that contact may be made to harmonic circuits as well as to the fundamental frequency. As in the previous illustrations the shaded portions are connected to the side of the circuit represented by I1. The small insulated circular areas are differently marked to indicate to which tone frequency they are electrically connected. Those marked in the same manner as the areas desigmated fl are common to the fundamental, while f2, f3 and fl indicate the order of harmonic frequency to which such areas are connected, respectively. The contacts are electrically connected to harmonically related sources in the same manner as are the various contacts shown in keying devices I6a, IBb, etc., in Figures 2 and 3. By placing the finger on that portion at the bottom of the illustration where only contact with ,fI and Il is possible the resultant tone will contain only the fundamental frequency whereas contacting the upper portion of the key will complete the connection to various harmonic frequencies as well as to the fundamental. The amplitude and number of harmonics will be relative to the area exposed to the touch. This will permit a variation in tonal quality or color by the addition or elimination of harmonic content by moving the finger over the key.

Figure 3 shows in a more simplified form all of the features previously described and in addition a means for obtaining tone-color by frequency modulation of the generated frequencies to accomplish a vibrato effect. This may be accomplished by including in the oscillatory circuits of each generator a device well known to those versed in the art as a magnetic modulator. This device 32 consists essentially of a three branch core 32a, upon the center branch of which is a controlling circuit winding 32h supplied with modulated direct current from source 5 and variable low frequency generator 30 as indicated or merely by the latter source. The frequency of pulsating or alternating current supplied by 30 will correspond to the frequency of the vibrato and will be for ordinary effects between two and ten cycles per second. By means of frequency control 46 located conveniently to the player the vibrato frequency may be readily varied. The magnetic polarities of controlled circuit windings 32o and 32d are such that none of the flux produced by the tone frequency currents in these windings will flow through the center branch upon which is 4winding 32h, thereby impressing one current on the other and, yet, obtaining zero magnetic coupling between the controlling and controlled circuits; thus, preventing intercoupling, or reaction, between tone frequency generators of the system. 326 is a variable impedance shunted across winding 32h to permit variation of the voltage across this winding. In the event a pulsating or modulated direct current is used in this circuit impedance 32h may also be used` for mak-lng slight adjustments in the frequency generated by the tone generator or oscillator I. This is accomplished by regulation of the ux density in core 32a which is one of the factors determining the frequency of oscillations generated by I. I do not wish to be restricted to the exact arrangement shown in this illustration. The vibrato modulating circuit may be coupled in a similar manner to any portion of the oscillatory circuit and have ultimately th same desired effect. Likewise the means for tone frequency adjustment will be effective in either of these schemes.

I do not wish to be restricted to the exact means and circuit arrangement shown on the drawings. Identical results may be similarly produced by variations in capacity or by variations in inductance and capacity in combination, said variations occurring at a rate corresponding to the vibrato frequency. Also, there may be included additional means for combining with the above described frequency modulation system, means for producing a variation in amplitude with' constant or variable phase relation with respect to the frequency modulation. The amplitude modulation component may be produced by the use of circuits and devices well known to those versed in the radio-electrical art.

An arrangement of controls 26, 21 and 28 is shown connecting respectively to amplifier 2i, v-band lters 22 and speaker selector 23, said controls to be located at some point in a concert hall Where the rendition of the music may be best judged or analyzed for the purpose of eecting changes in relative volumes of the various tone frequencies produced by this and like instruments. Provision is also made for telltale indicators at the conductors stand or withinthe vision of the players, to indicate the relative volumes -and the corrections as' applied from the monitoring and listening station. These controls and indicators may be of a type well known to those familiar with the electrical art. Impedance device 33 may be inserted in some portion of the keying circuit where intermittent currents occur to reduce the undesirable eiects known as keying transients or key thurnps. In this invention wherein tone frequency generators or electronic tube oscillators are used as prime sources of alternating current and the keying is accomplished in the coupled output circuits there is a much greater freedom from keying transients than will be found in instruments wherein keying is done by interruption of the oscillatory circuits or in the power supply connections. In my keying arrangement the current and voltage amplitudes at the points of interruption are relatively small Acompared to those found in previous systems.

I claim:

1. In an electrical musical instrument for incepting and modulating tone-frequency currents: a plurality of sources of tone-frequency currents; a source of vibrato-frequency current; and means for impressing said vibrator-frequency current on said sources of tone-frequency current so as to produce vibrato eiects therein and for 'preventing reaction of said tone-frequency current upon said source of vibrato-frequency current, said means comprising a magnetic modulator.

2. In an electrical musical instrument for incepting and modulating tone-frequency current: a plurality of sources of tone-frequency current; a source of vibrato-frequency current; and means comprising a magnetic modulator and variable impedance associated with said modu- V lator for impressing said vibrato-frequency curcepting and modulating tone-frequency currents: a plurality of sources of tone-frequency currents;

a source of vibrato-frequency current; and means for impressing said vibrato-frequency current on said plurality of sources of tone-frequency currents so as to produce vibrato effects in said tone-frequency currents and' for preventing reaction of any of said tone-frequency currents upon any of said sources, said means comprising a magnetic modulator.L

4. In an electrical musical instrument for incepting and modulating tone-frequency currents: a plurality of sources of tone-frequency currents; a source of vibrato-frequency current; and means comprising magnetic modulators and variable impedances associated with said modulators fo'r impressing said vibrato-frequency current on said plurality of sources of tone-frequency currents so as to produce vibrato effects in said tone-frequency currents, for preventing reaction of any of said tone-frequency currents upon any of said sources, and for regulating the frequencies of said tone-frequency currents.

5. In an electrical musical instrument, the combination of an oscillating vacuum tube circuit having capacitative and inductive reactances, the values of which control the frequency of oscillation of said circuit, and vibrato frequency generating means coupled to one of said reactances and operable periodically to vary' the effective value thereof, thereby periodically to vary the frequency of the current generated in said oscillating circuit to produce a vibrato eff ect.

6. In an electrical musical instrument, the combination of a plurality of oscillating vacuum tube circuits each having capacitative and inductive reactances determining their respective frequencies of oscillation, and vibrato frequency generating means coupled to one of the reactances of each of said circuits and operable periodically to vary the eective value thereof, thereby periodically to vary the frequencies of the currents generated in said oscillating circuits to produce a vibrato effect.

7. In an electrical musical instrument in which electrical generators of the frequencies of the musical scale are utilized to supply energy to an output circuit having means to translate electrical oscillations intosound; a keyboard comprising an insulating member, and a plurality of electrical contacts mounted on said insulating member and arranged to control the transmission to the output circuit current from generators of substantially harmonically related frequencies, said contacts being spaced suiiiciently close together that a plurality of them may be simultaneously contacted by a linger of the player and thereby selectively determine the tone quality of the note which is sounded.

8. In an electrical musical instrument for incepting and modulating tone-frequency currents, a plurality of sources of tone-frequency current, each of said sources comprising a vacuum tube oscillator having a frequency controlling impedance, a source oi' vibrato-frequency current, and means for impressing said vibrato-frequency current on said impedances of said sources oi! tone frequency current so as to vary the values of said impedances and thereby to produce vibrato eiects in the current generated by said sources.

9. In an electrical musical instrument for incepting and modulating tone-frequency current, a vacuum tube oscillator having an impedance the value of which is a factor in determining the frequency ct oscillation of the oscillator. said oscillator forming a source of tone-frequency current, a source of vibrato-irequency current, and means for impressing said vibrato-frequency current on said impedance o! said source of tone- Irequency current so as to produce vibrato etects therein and for preventing reaction oi said tonefrequency currents upon said source of vibratofrequency current, said means comprising an element which periodically varies the eilfectiveness of said impedance.

CHARLES E. WILLIAMS.

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