US2147948A - Apparatus for the generation of musical tones - Google Patents

Description

Feb. 21, 1939. E L. KENT ET AL 2,147,948

APPARATUS FOR THE GENERATION OF" MUSICAL TONES Filed Aug. 10, 1936 4 Sheets-Shed 1 "hullnF w NIIMIH INVENTORS 5 9 Ear/e Line/7t j W-- Le/e ycPas/a --wwlllll}' ATTORNEY.

Feb. 21, 1939 E L. KENT ET AL 2,147,948

APPARATUS FOR THE GENERATION OF MUSICAL TONES Filed Aug. 10, 1956 4 Sheets-Sheet 2 IN VEN TORJ Ear/e L. Ken 2" 0k Lefiay C. Has/a y A TTORNEY.

\Feb. 21, 1939. E 1.. KENT ET AL v APPARATUS FOR THE GENERATION OF MUSICAL TONES' Filed Aug. 10, 1936 4 Sheets-Sheet 3 lllllllllk W 9% W T N m m m/k 2 Feb. 21, 1939. E L. KENT ET AL APPARATUS FOR THE GENERATION OF MUSICAL TONES Filed Aug. 10, 1936 4 Sheets-Sheet 4 0a R Y WM WM L E C. 0 Wh f n I a A E e 0 a MU Q N w ohN km M fi .W h m \MN ma R5 A. F Eb hum & IIMII H W um Q Patented Feb. 21, 1939- 2,147,948

UNITED STATES PATENT OFFICE APPARATUS FOR THE GENERATION OF MUSICAL TON ES Earle L. Kent, Manhattan, Kans and Le Roy 0. 1 Paslay, Kansas City, Mo.; said Paslay assignor to said Kent Application August 10, 1936, Serial No. 95,056 11 Claims. (Cl. 84-1) Our invention relates to apparatus for the gen- Another object of our invention is to provide eration of musical tones and more particularly a method of and apparatus for producin con to an electric organ or organlike musical intinuous musical tones in which coupling maybe strument. obtained in a simple and expeditious manner;

A musical tone has two distinguishing charac- Another object of our invention is to provide teristics namely pitch and timbre. The pitch an electric organ in which the tremolo of ton of a tone depends upon the rate of vibration prois controllable by the musician both in intensity duoingit. The timbre of atone depends upon the and in speed enabling the tremolo to have its wave form of the vibration. Many attempts greatest effect upon the higher tones. have been made to reproduce musical tones of A further object of our invention is to provide in predetermined timbre, but no practical method an electronic organ having a plurality of manhas been heretofore developed. Many schemes uals in which the volume of each manual is conwill produce notes of the desired pitch but the trollable in the usual manner, as well as having been accomplished only by photoelectric methods Another object of our invention is to provide it One object of our invention is to provide a A further object of our invention is to promeans of and apparatus for producing any convide an instrument in which the pitch will not tinuous tone with extreme fidelity. vary when used on any modern power line.

Another object of our invention is to provide A further object oi our invention is to protones similar to the timbre of the finest octave harmonics, enabling the organ to "wear well with tones in the organ may duplicate the timbre of tempered harmonics and the true harmonics supcontent over the range may be varied, thereby appear from the following description.

parts in the various views; Figure 1 is a. portion 01' a schematic drawing Another QbJect of our Invention to prfmde showing one means for practicing the method of an electric organ containing a complete specification of stops. 16 foot, 8 foot, 4 foot, and 2 foot fi f igzi and embodying one form of our r Figure 2 is another portion of a schematic such as 32 foot, 10% foot, 1% foot, 1 foot, 1% foot, and celeste stops are possible with but small drawing part of whlch is sh9wn in Figure cording to the specifications of the American our invention. Guild of Organists may be used. Figure 5 is a sectional-view, taken on the line a predetermined timbre and-pitch 5--5 of Figure 4, showing the scanning bars of the rotor of the converter shown in Figure 4.

Figure 6 is a sectional view taken on the line 6-6 of Figure 4, showing the capacity islands on the stator.

Figure '7 is a sectional view taken on the line 1-4 of Figure 4, showing the capacity rings on the rotor.

Figure 8 is a sectional view taken on the line 8--8 of Figure 4, showing thecapacity rings on the stator.

Figure 9 is an enlarged tion of the stator face. in Figure capacity island.

Figure 10 is a partial schematic view, showing another embodiment of our invention in which the predetermined pitch and timbre are imposed upon a carrier wave by means of frequency modulation.

Figure 11 is a partial schematic view showing another embodiment of our invention in which are imposed upon a carrier wave by means of phase modulation.

Figure 12 is a vector diagram showing a portion of the currents in the form of the apparatus shown in Figure 10 plan view of a por- 6 showing a In general, our invention contemplates the generation of a high frequency carrier wave, the modulation of said high frequency carrier wave by mechanical means in accordance with a wave form having predetermined characteristics both as to frequency and form and the subsequent demodulation of said modulated carrier wave to obtain an electrical wave having the desired predetermined characteristics, and the conver-' sion of said electrical wave into an acoustic wave having the characteristics of the predetermined wave form.

In our method and our apparatus we employ a high frequency current. A high frequency current is necessary in order to carry out the method of and employ the apparatus of our invention. In addition however, high frequency current has many advantages which will be hereinafter more fully pointed out. A tuned circuit resonating at the frequency of a high frequency current presents a very high impedance to its passage, while permitting high frequency currents of other frequencies to pass readily.

In its simplest aspect our apparatus comprises a superaudio generator producing a carrier wave impressed upon a tuned circuit, tuned to the frequency of the super-audio generator through a variable capacity adapted to modulate the carrier wave in accordance with a predetermined wave form, either by amplitude modulation, frequency modulation, or phase change modulation, as will be hereinafter more fully pointed out. The circuit is adjusted so that parallel resonance occurs in the entire circuit, eliminating the deleterious effects of capacity to ground. In this manner, a very small capacity change will effect a large n 'jdulation of the carrier More particularly referring now to the drawings and especially Figure l, thermionic tube I is connected as an oscillator to produce a superaudio frequency wave, the frequency of which may be controlled by means of a crystal 3. The super-,audio signal generated by the oscillator is amplified by thermionic tube 4, which isconnected as an amplifier. It is to be understood that any suitable stable means may be used for the generation of the high frequency voltage.

The output of the amplifier is loosely coupled to coils 5, 6, and 1. Coil 6 is center tapped by conductor 8 which is grounded at 9. The ends of coil 6 are connected to conductors III and II which are leads passing to the first manual of the instrument.

Thermionic tube I2 is connected similarly to thermionic tube I to produce a super-audio frequency of a different frequency however, than tube I. This frequency is controlled by crystal I3. The output of tube I2 is amplified by thermionic tube I4, the output of which is loosely coupled to a coil I5 which is center tapped by lead I6 to ground I'I. Theleads I8 and I9 to the second manual of the instrument are connectible by switches 20 If switch 20 is thrown upwardly to make contact with contact point 22 and switch 2| is thrown downwardly to make contact with contact point 23, some energy from oscillator I through coils 5 and 1 is fed in series with the output of oscillator I2 to the leads I8 and I9. In this manner, two frequencies are fed to the second manual of the organ so that, when the keys in this manual are played, it will be the same as though the first manual and the second manual were being played in unison, as will hereinafter be more fully described. In pipe organ practice it is desirable not only to couple in unison but also in other arrangements.- This is usually taken care of in a pipe organ console in the construction. The need for couplers came about chiefly because of the lack of sufflcient pipes, it being cheaper to couple than to put in duplicate pipes.

In the instant invention, it is possible to obtain a large number of pipe equivalents so economically that coupling need not be resorted to unless desired.

When the switch 20 is in contact with contact point 24 and the switch 2| is in contact with contact point 25, the high frequency voltage generated by tube I2 and amplified by tube I4 is directly coupled by coil I5 to the leads I8 and I9.

Thermionic tube 26 is connected similarly to thermionic tubes- I and I2 to produce a high frequency voltage. Its frequency, however, is different from that generated by tubes I and I2 and this frequency is determined by the tuning of the circuit and is controlled by the crystal 21. The output of the oscillator 26 is amplified by the thermionic tube 28 and the amplified, high frequency voltage is loosely coupled to coil 29 which is center tapped by lead 30 to ground 3|. The ends of coil 29 are connected to conductors 32 and 33, which are leads passing to the third manual of the instrument.

It is to be remembered that, in the schematic showing in this specification, a limited number of parts will be shown as illustrative of the principle and the construction to enable those skilled in the art to practice our invention. The showing and description are not to be construed by way of, limitation but for purposes of illustration only. By using a number of different frequencies, additional manuals may be obtained.

' Across the leads I0 and II of the first manual, I9 and I8of the second manual, 32 and 33 of the third manual are a plurality of parameters, one for each key of the manual. For simplicitys sake, we have shown only four keys to a manual, it being remembered that the showing is diagrammatic only, for purposes of illustration. It is possible to have any convenient number of octaves in a manual and we will show a converter which can be readily used to obtain a Since the parameters are center tapped, no voltage will be impressed upon the leads 46, 41,

reference numerals 38, 39, 40, and 4|. meters in the third manual are designated by reference numerals 42, 43, 44, and 45. meters are center changed. When a key,

48, 49, 50, 5|, 52, 53, 54, 55 56 and 51 respecstood is closed, through lead 19, key 69, contact tively. The parameters have impedance characpoint 80, lead 9|, resistance 82, high frequency 10 teristics which vary with current. The parachoke coil 83 through conductor 46 through the meters may be light bulbs, Thyrite or any maleft hand section of parameter 34, through conterial whose impedance varies with the current. ductor i0, througn one half of coil 6 through Light bulbs are We prefer to use 'I'hyrite impedance is practically change in curren parameter 34, which are in parallel, until the condenser The time con- 84 attains its charge.

ers. It is an insulation at one voltage and an excellent conductor at another voltage. ristance is a function of voltage, the resistance decreasing and the current increasing approximately 12- times each time the voltage is doubled. This rule is applicable, regardless of the rate of change of voltage and there is no time lag. The resistance depends of course upon its thickness.

The converters imparting to the high fre quency carrier war a predetermined e are shown diagrammatiscanning arms 62 pass closely adjacent to the cally in Figure i and will be hereinafter more various stator islands so that the high frequency fully explained In general, a converter consists current will flow to charge the stator islands of a scanning arrangement having a plurality of The coupling will vary as the pro ected area of arms comparatively long with respect to their scanner arm 62 upon the stator island, since the width Such scanning devices are shown diastator islands are made of such shape that they grammatically in Figure 1 and designated by refwill give a predetermined timbre to the carrier erence numerals 58, 59, 60, and 6|. The arms wave In the form shown in Figure 1, the ar- 62 of the scanners act as one plate of a condenser rangement is such as to give amplitude modulaand are adapted to scan islands 63, 64, 65, and 66 tion to the carrier wave, the voltage transmitted of the respective converters These islands will varying as a function of the projected area bebe hereinafter more fully described in connect on tween a scanner arm 62 and the island. It is with the description of the converter. They act important to notice, at this point that the scanas other plates of condensers and are adapted to ner arm 62 is comparatively narrow with respect give a varying capacity with scanner arms 62 to the island. The importance of this feature Capacity islands 63 will give the timbre of the will be hereinafter more fully explained diapason, one of the two fundamental tones of The distance between adjacent scanner arms an organ. Capacity island 64 will give the timbre 62 is exactly equal to the length of each island of the cello. Capacity island 65 will give the so that, as soon as one scanner arm leaves an timbre of a violin. Capacity island 66 will give island, the other is ust starting to scan the the timbre of a harmonic flute. High frequency island The frequency with which the scanner current is passed to the scanners by manual couarms pass over an island determines the pitch of pling Each of the respective converters is prothe note produced as will hereinafter be more vided with a capacity coupling ring 61 to which fully described. the leads of the first manual are connected The method of keying just described has sev- Lead 68, energized by key 69, is thus adapted to eral advantages. It is possible to use a standard be coupled to the scanner 58. Lead 10, energized organ console with all of its coupling and piston by key 1| is thus adapted to be connected to features. It is likewise possible to control the scanner 59. Lead 12, adapted to be energized by response of the tones for staccato or legato effects key 13 is thus adapted to be coupled to scanner y changing the time constant of condenser 84 68. Lead 14, energized by key 15, is thus adapted for each key The use of direct current which to be coupled to scanner 6|. is isolated from the tone producing high fre- There are twelve converters, since there are quency current makes it possible to separate the only twelve notes in an octave. By using a plutone producing unit in the console without noise rality of scanners with corresponding islands, it pickup It is only necessary to key a small is possible to obtain a plurality of octaves upon amount of power so that there will be substan- 70 It is also possible to obtain various pitches, varying from each octave with a single scanner by of the islands. This will be fully explained.

other by a whole varying the shape hereinafter more from the frequency of its be understood, of

' 32.70 for C in the be produced by the converter having scanner 59. The frequency of each note in the scale differs adjacent note by the twelfth root of 2. The following table will give the frequencies for the notes of the scale for six octaves, together with the revolutions per second made by a scanner similar to that shown in Figure 5 and the pulley diameter in inches to be used on the driving motor shaft at a speed of 20 revolutions per second of the motor. In each case in the following table the rotor pulley is 8 inches in diameter. The speed of 20 revolutions per minute for the driving motor is obtained by using a 6 pole synchronous motor with a 60 cycle alternating current found almost universally throughout the United States. It is to course, that any ratio of motor pulley diameters can be worked out the desired result.

speed and to achieve change of amplitude will vary as the rotor speed and the number of scanner arms. Each of the capacity islands is connected by a conductor to a tuned circuit. Conductor 90 connects each of capacity islands 64 to a tuned circuit 9|. Tuned circuit 9| has coupled thereto circuit 92 and circuit 93 and the tuning of all three circuits is such that a high impedance to ground 94 is presented to each of the three frequencies generated by oscillators I, I2, and 26. In other words, the circuit is triple tuned. The arrangement makes it possible to tune out the stray capacity to ground of the lead 90. Loosely coupled to coil 95 of the tuned circuit 9I is a coil 96 making it possible to mix energy from the tuned circuit 9| into tube 91. A stop switch 98 is adapted to place coil 96 in a circuit for impressing energy picked up thereby upon the grid 99 of tube 91. This occurs when the switch makes contact with contact point Tempered Musical Scale A-440 International Standard Motor First Second Third Fourth Fifth Sixth Rotor 59g? octave octave octave octave octave octave R. P. S. 20

R. P. S.

It will -be observed by reference to the above table that if there are 10 scanning arms for example upon the C-rotor, the frequency of first octave is obtained. An octave higher can be obtained by the use of 10 scanning arms by making the wave form exactly half the distance between duplicating the wave form.. In this way, one wave form will be scanned twice by a single scanning arm so that a single wave form will be scanned 20 times for each revolution and, since there are 3.210 revolutions per second being made by the rotor, the frequency of 65.40 cycles per second will be obtained. Doubling the number of scanning arms will double the frequency of the wave form and will raise the pitch one octave. By the use of single and double wave forms, it is possible to obtain 6 octaves with 3 sets of scanning arms as will be hereinafter more fully explained. Each of the keys 86 of the second manual of the instrument operates similarly to key 69 and the operation of the keys 86 is adapted to selectively charge capacity coupling rings 81 of each of the 12 rotors. The voltage impressed upon the coupling rings 81 may be either that generated by oscillator I2 or a mixed voltage generated by both oscillators I and I2, depending upon the positions of switches 2I and 20 as hereinabove described. Similarly, keys 88 of the third manual of the organ are adapted to selectively oscillator 26 to respective capacity coupling rings 89 of the rotors.

The capacity islands are charged with high frequency voltage, the charge being determined by the capacity coupling between a scanner arm and that portion of the island projected by the scanner arm. The voltage, therefore, will vary in amplitude as a function of the shape of the capacity island being scanned. The frequency ofthethe scanning arms and a charge the voltage generated by I00. It will be noted that the arm of switch 98 is contacted with contact segment IOI when the switch is in open position. This completes the main line from ground I02 to grid 99. The construction is such that contact is made with contact point I00 before 'the' switch arm moves off from contact with segment IOI. Stop switch 98 determines whether or not energy will pass from tuned circuit 9| to the tube 91. A similar stop switch I03, adapted to complete the circuit from ground I06 through a loosely coupled coil I04 by making contact with contact point I05 and completing the circuit from ground I06 through a conducting segment I01, is provided. A stop switch I03 is adapted to connect coil I04 to the grid I08 of tube I09 through conductor IIO. Similarly, a stop switch 'I I I is adapted to place loosely coupled coil H2 in connection with the grid II3 of tube 4, through conductor II5 when contact is made by stop switch III with contact point 6. A contact segment II1, similar to contact segments IM and the main line to ground I I8, whenthe stop switch is in open position. Capacity islands 63 of each of the 12 rotors are connected by conductor II9 to a tuned circuit I20, the inductance I2I of which has coupled thereto tuned circuits I22 and I23, tuned circuits I20, I22, and I23 being tuned together to give a tuned circuit which is triple tuned so that the imp'edances'of the circuit I20 to ground I24 is high to each of the three peaks of resonance to which the circuit is tuned. The tuning, of course, as in circuit 9I, is to the frequencies generated by oscillators I, I2, and 26. The island 63 will give the timbre of the diapason. If it is desired to play the diapason in manual 1 only, the stop switch I25, similar to the stop switch 98, is moved to closed position to make contact with contact point I26. This places coil I01, is provided for completing 15 I'll t I21 to loosely couple energy from coil I2I,

which energy will be passed through conductor I28 to the grid 99 of tube 91 to which the energy from generator I is passed, as will hereinafter be more fully explained. If it is desired to play the diapa'son in manual 2, stop switch I29 is moved to make contact with contact point I30, thus loosely coupling coil I3I with coil I2I so that energy from the oscillator I2 will pass through conductor IIO to grid I08 of tube I09 to which the energy from generator is desired to play the diapason in manual 3, stop switch I32 is moved to/make contact tact point I33 to loosely plete the circuits from grid to ground similar to contact segments IOI, I01 and Ill. islands 66 of all of the, rotors are connected to conductor I31 which leads to a tuned circuit I38. This circuit is tuned to the frequency of oscillator oscillator I so that, if an island 66 is scanned by the frequency of oscillator I, energy may be coupled from coil I40 to coil I4I as when circuit i 38 is resonating the impedance to ground is very high. Islands the frequency of oscillator are provided for coupling coils to said tuned circuit to the grid II 3 of tube II 4.

Plate-ISI of tube 91 is connected in a. circuit containing a tuned circuit I52 which is tuned to The plate I53 of 26, and stop switches Tubes 91, I 09, and II4 are connected to their respective leads I28, H0, and H5, through blocking condensers I51, I58, and I59. The tubes 91, I09, and I I4 are shown as pentagrid mixer tubes. The tubes can be of any suitable type such as ception that the plate circuit in tube Taking tube 91 astypical. the energy is fed to theflrst control signal passes from tube I 66 to a. switch is adapted to make contact with either contact point I68 or contact point IE9.

The volume control,

and third manuals of the Tubes I09 and I I4 are in all respects similar to tube 91 just described,- with the ex- I09 is tuned to the frequency of oscillator I2 and the plate circuit in tube II4 is tuned to the frequency of oscillator 26. The full wave detector and amplifier for tube I09 is tube I13 and the full wave de- I15 by moving switch I85 into contact with con.- tact point I86 Likewise, the output of full wave detector and amplifier I14 can be passed to conductor I 15 by moving switch I81 into contact with contact point I88.

If switch I61 is moved into contact with contact point I68, the energy passes through conductors I90 and MI to the first control grids I92 and I93 of tubes i9t and I95. The output of tube I95 passes from ductor I91, selective filter I99 having the following characteristic.

blocking condenser 2M passed to a scanner rotating at a the detector, will not I61 controls the tremolo for the first manual. If switch I is moved to make contact with contact point ZIU, tremolo is given to the second manual as the output of tube I13 then passes to conductor I through conductor 2| I. If switch I81 is moved to make contact with contact point 2I2, tremolo is then had on the third manual of the instrument, since the output of tube I14 then passes to conductor 2 I 3, thence through conductor 2| I to conductor I90. In this way, tremolo may be put upon eachmanual independently.

Individual stop control is easily obtained by changing the voltage of stop pickup coils 96, I04, II2, I21, I3I; I34, MI, and I49. This voltage is easily adjusted by the degree voicing an organ to an auditorium, it is very desirable to be able to set the ma um value on each stop separately. This can easily be done with ourarrangement.

It is' believed that the operation of the foregoing modification shown in Figures 1, 2, and 3 will be clear from the foregoing description. A high frequency current is generated, which is predetermined speed and having a predetermined number of scanner arms. These scanner arms pass the islands having a predetermined form and charge the same with a high frequency current with an amplitude varying as the capacity coupling varies. The energy from the capacity islands is selectively picked up by the operation of stops and is demodulated, amplified and sent to a loud speaker directly or through a channel which imposes a tremolo upon the tone. The stops in each manual may be controlled as to volume and the tremolo may be selected for each manual. By the operation of switches 20 and 2|, a plurality of manuals may be played in unison by operating the keys of one manual.

The keys select the pitch, that is, the particular notes in the particular octave to be played, while the stops select the particular instrument or instruments to be played. If a number of stops are put in operation, the pressing of a key of a manual will play a number of instruments in unison. It will be observed that our instrument can be made more varied in resources than the largest of organs, not only producing all known musical instruments but being able to produce new sounds by drawing arbitrary timbres not now producible by any known instrument.

At this point, we would like to call attention to the importance of high frequency current in our invention. Wth a high frequency current, we are enabled to obtain a higher gain per stage of amplification than is possible at audio frequency. There is also less trouble with frequency discrimination by obtaining amplification of the high'frequency carrier wave. frequency current enables the elimination of extraneous noises which are due to audio pickup. Such an audio frequency as a 60 cycle .hum, for example, which is picked up in be passed along with the high frequency current. We obtain our modulation by scanning an insulated plate having a desired wave form. By using high frequency current, the shape of the island will govern the shape of the wave form since the voltage output will vary directly with the area covered by a scanning bar and is not dependent upon the rate of change of area or upon any known linear function. This has an additional advantage since the output of our converters, not being dependent upon the rate of change of capacity, the'strength of of coupling. In

The use of a high the circuit before low tones will be the same as the high tones. any tone which would be obtained would have rate change of capacity. With direct current, therefore, the high tones will have a much greater output than the low tones, making the design complicated for overcoming making it difficult in general to obtain a sufficiently high level for low tones.

By using high frequency current, we are enabled to employ very small converters. By means of tuning or resonance, eliminating the voltage divider effect of stray capacity, able to obtain a high output from a converter. The same converter unit may be used for several manuals since carr'er currents can be mixed and separated as they are in telephony, making it possible to obtain the maximum intelligence from the smallest space. The use of high frequency currents makes it possible to obtain a greater impedance change in a small space. High frequency current enables capacity coupling to be used for keying or for stopping.

Referring now to Figures 4, 5, 6, '1, 8, and 9, our organ normally employs 12 converters. Each of the converters may be identical in construction, thus simplifying the manufacture, the pitches being obtained by using different sized pulleys upon the motors. If desired, one motor having a shaft with 12 different sized pulleys may be employed. 12 individual motors of smaller size may be employed, each driving a single converter. If celeste efiects are desired, additional converters operating at a s 'ghtly different speed may be employed so that a note may be sounded at two slightly different frequencies to produce beats giving the celeste effect.

The rotor 25d of the converter is keyed to a. shaft 25I by key 252. To the shaft 25I is keyed a pulley 253 for rotating the shaft 25L The shaft operates on ball bearings 254 and is housed in a two-part casing 255, held in assembled position' by bolts 256. In making the converters, we took oscillograms of the tones which we wished to reproduce. The oscillograms may be taken with a cathode ray oscillograph or with a string galvanometer type of instrument. After recording the wave shape on film, the film was placed in an enlarging machine and one cycle of the particular tone was reproduced on rectangular coordinate paper. A circle was then drawn on drawing paper and divided into a number of equal spaces as accurately as possible. The tone wave shape was then transposed from rectangu :lar coordinates to polar coordinates, placing it in its allotted place on the drawing. This transfer was done with a pair of proportional dividers, 'one point at a time every few degrees along the curve. The drawing was made three times actual size in order to obtain accuracy when reduced. The line widths were checked with a Brinell microscope for uniformity. A drawing was then made for the rotor to correspond with the stator. The construction of the rotor was such that scanning bars pass in succession over a stator island so that, just as one scanning bar leaves an island, another bar starts'across, that is to say the distance between scanner bars is exactly equal to the width of an island. The bars were made of such width as to offer a maximum area without exceeding the point where important harmonic the unbalance and v we are tone oi island fundamental cycle is one inch long and the tenth harmonic is the largest or highest harmonic to be produced be had in proportion with this width. It is essential that the bars be of uniform width and spacing in order to produce a uniform continuous tone.

scanning bars. taves in unison effect of a 4' using the cycle on an oscillograph stop and a as a 4' and got the stop combined, by

it was printed with an arc lamp to permit the light to harden the enamel everywhere except where the lines ap- Upon development, the lines were washed out, exposing a copper surface where the showing through.

Island 260 represents a synthetic tone on a l6 stop. Island 26l is the stop. Island 265 is the wave form of a philomela 8' stop. Island 266 is the wave form of a diapason 8' stop. Island 261 is the wave form of an 8' stop of vox humana. Island 268 is the wave form of an 8' stop oboe. Island 269 is the wave form of an 6' stop of a harmonic flute. Island 216 is the wave form 01' a clarinet on an 8' stop. Island on an 6' stop. Island 212 is the wave form of a horn on an 8' stop. Island 213 is the wave iorm'of a flute damour on a a diapason 4' and 2' stops. Island 216 is Island 211 is a the same synthetic tone as island 211 on an 6' stop. Island 219 is the synthetic 266.0n an 6' stop. Island 266 is Island 215 is a cello a synthetic tone on an 6' stop.

give a tone used to give the same timbre as island 282, an octave lower.

has the same wave form as island 261. Island 298 has the same wave form as island 268. Island 299 has the same wave form as island 269. Island 300 has the same wave form as island 210. Island 301 has the same wave form as island 21L Island 302 has the same wave form as island 212. Island 363 has the same Island 304 has the The copper rings 3I3, 314, by the scanning rings are be accomplished si very easily by placing the scanning rings on each side of the rotor 256 or by making the rotors of a slightly larger diameter; and placing a larger number of scanning rings thereon. The spaces 322, 323, and 324 between the coupling rings are grounded as shown in Figure 4 by conductor 325, at ground 326. The energy is adapted to pass from coupling ring 61 to coupling ring 321 by capacity coupling. Energy is adapted to pass from coupling ring 89 to coupling ring 328 by capacity coupling and energy is adapted to pass from coupling ring 81 to coupling ring 329 by capacity coupling. Coupling rings 321, 328 and 329 are shown in Figure 7 and are positioned upon one face of the rotor 256. The spaces between coupling rings 321, 328 and 329 are connected to the conductor 3'I6, which goes to ground 3I1. Coupling ring 321 is directly connected by a conductor to scanning ring 368. Coupling ring 326 is directly connected by a conductor to scanning ring 369, and coupling ring 329 is directly connected by a conductor to scanning ring 3I6. This can readily be seen by reference to Figure 4.

It will be seen that keyed energy passes to the coupling rings in the stator through conductors, to the coupling rings in the rotorby capacitycoupling, to the scanning rings by direct connection, from the scanning rings by capacity coupl n capacity islands energy through demodulation channels into an acoustic wave either with or tremolo, as hereinbefore described.

The grounding of the copper around theislands and around the scanning rings shields the islands and prevents distortion due to fringing.

In operation, high frequency voltages are generated by each of the oscillating tubes I, i2, and 26, and impressed upon the respective manuals of the organ. When it is desired to play a note, a key is pressed. As long as the keys are open, the high frequency voltage is passed to parameters each of which is center tapped by a lead to a stator coupling ring. voltage will fiow until the balance in the parameters is changed. For example, if scanner 56 is on a C-rotor and it is desired to play a C in the first manual upon a diapason, the key 69 is pressed, permitting direct current to flow from the battery 11 through the key 69, through the center tap 46, through the left hand portion of parameter 34, through conductor I6, through one portion of coil 6, through conductor 8 to ground 9, thence to the other side of the battery. The passing of direct current through the left hand portion of parameter .34 disturbs the balance permitting the high frequency voltage to fiow from coil 6 through the lead I6, through the left hand side of parameter 34, through center tap 46, through lead 68, to capacity coupling ring 61 of the C-rotor. charge a coupling ring upon the rotor which is directly connected to the scanner ring 56, having scanner arms 62. The scanner arms 62 will charge the capacity island 63 representing the diapason, as well as all ofthe other capacity islands scanned. The carrier wave envelope will be changed in accordance with the wave form of island 63 and at a speed determined by the num-' ber of scanning arms and the speed of rotation of the rotor of the converter. The arrangement is such that the pitch will be to give the note C. Stop switch I25 has been pulled to make contact with contact point I26 to give the diapason upon the first manual. The high frequency voltage thus modulated by the converter will be imis selectively passed for conversion without but also acts as to the capacity islands, and from the- Being center tapped, no

' island as the other plate, is in parallel with capac- The capacity coupling ring will' pressed upon the tuned circuit I26. The tuned circuit I26 is triple tuned so that it will presenta high impedance to ground for the frequency of generator I as well as generators I2 and 26. Energy of the modulated carrier waveis picked up by coupling coil I21 and impressed upon the pentagrid mixer tube 91 through lead I26. Here the volume control I16 will determine the volume of the note. Tube 91 acts not only as an amplifier a frequency selector having a plate circuit tuned to the frequency of generator oscillator I., The tuned output of tube 91 passes to tube I66 which acts as a full wave detector and amplifier. The output of tube I66 may be passed directly to an audio amplifier for conversion into an acoustic wave by a loud speaker which acoustic wave will have a predetermined pitch and timbre in accordance with the characteristics impressed upon the carrier wave by the converter. If it is desired to add tremolo, the output of tube I66 is passed into tubes I94 and I95 by means of switch I61. The incoming signal goes to the first control grids of the tubes. The second control grids of the tubes are impressed with a low frequency alternating current in order to impart'a t tremolo. The output of the tubes will pass to respective filters, one of which has a characteristic of varying the attenuation directly as a function of the frequency, and the other of which has a characteristic'of varying attenuation inversely as 1 a function of the frequency in order that higher frequencies may be given more tremolo than the low tones.

If desired, energy from a plurality of generators may be mixed so that the operation of the keys 3 of one manual will give the effect of a plurality of manuals played in unison.

In the above operation, which has reference to Figures 1 and-2, the wave form of predetermined characteristics is impressed upon a high frequency carrier wave by means of amplitude modulation.

Referring now to Figure 16, a simplified schemiatic showing of an arrangement to give frequency modulation is shown. The tube 466 is an oscillator having a capacity 46I in the circuit to govern. its frequency. A capacity island 462 is scanned by a scanning ring 463 having scanning arms 464. Thelcapacity of the condenser formed by a scanning arm as one plate, and the capacity When a key 465 is actuated, the capacity of the converter is placed in parallel with the capacity governing frequency of the oscillating tube 466, so that the frequency of the oscillator will vary in accordance with the variation of the converter. The output of the converter is inductively coupled to a tuned circuit 466 which is tunedto the original frequency of the oscillator. The coupling between the tuned circuit of the oscillator and the tuned circuit 466 will vary as the frequency varies, that is, the transfer of energy will vary due to the frequency varying fro the frequency at which the transformer 461 wa peaked. The amplitude carrier wave is passed t an amplifying tube 468, the output of whic passes through a lead 469 to a demodulator fo demodulation and amplification, and conversio into an acoustic wave by loud speaker similar t that of the modification shown in Figures 2 and 3 In connection with the form of the inventio shown in Figure 16, it should be remembered tha in each case the modulated carrier wave is im presfised upon a tuned circuit, tuned to the fre que cy of the oscillator, that is, the frequency of carrier wave, in order that the tuned circuit ma pedance to ground for the frequency of the genplexity of the organ The stops are brought into erator 40, while permitting all other frequencies play in the conventional manner. Standard orto pass to ground without affecting the acoustic gan consoles complete, according to the specificachannel. tions of the American Guild or Organists may be Referring now to Figure 11 a simplified diaused. Coupling may be obtained simply. The

l ad 505, nd respective h r n p ne t strument will not vary when used on any modern d 0 a d fla ho 0 h a key 508 is power line since a synchronous motor sets the the open position, there is no voltage across the pitch The organ may be quickly changed from 12 as 51. The current flowing through'conductor 554, connected with the lower branch of coil 513,

ssible in a small s ace. which is coupled to the output of the oscillator W D It will be understood that certain features and sub-combinations are of utility and may be employed without reference to other.features and sub-combinations. This is contemplated by j "t voltage drop across reslstance and is within the scop of our claims. It is furshown and described.

Having thus described our invention, what we claim is:

1.111 an apparatus for generating musical sounds of predetermined pitch and wave form includim in combination a hi h freouency cur- 1 b D ed and net Voltage ER f result as shown by rent generator adapted to generate a voltage of a given frequency, a resonating circuit tuned. to

the converter and this will be a direct function of gf ig g'fg gg gf igi fiffi ug sfii sa e the wave form of the capacity island 5!? and the a musical instrument of great Wealth of resource and great flexibility, surpassing that of the ortermined wave form gan, The instrument is organlike in character frquency with a predetermined wave form, the other of modulatedto produce velocity,

10 between said elements, and means for converting the output of said tube into an acoustic wave of a frequency'at which the capacity of said condenser is being varied.

3. In a musical instrument, a 'source of high frequency.potential of predetermined frequency, a resonating circuit tuned to the frequency of said high frequency potential source, a variable condenser for coupling the output of said high frequency generator and said tuned circuit, said variable condenser comprising at least two plates, one of which is shaped in accordance which comprises a plurality of scanning arms relatively narrow with respect to the width of said plate of predetermined wave form, means for passing saidscanning arms over said plate of predetermined wave form at a predetermined and means for converting the output of said resonating circuit into an acoustic wave in sympathy with the 'wave form of said condenser plate and at a frequency determined by the speed at which said scanning arms pass over said condenser plate.

4. In a musical instrument in whicha high frequency current is generated, modulated in accordance with a predetermined wave form, de-

an electrical wave of said predetermined wave form, said demodulated wave converted into an acoustic wave of said predetermined wave form, a variable condenser comprising a pair of relatively movable members, one of said members supporting a capacity island shaped in accordance with apredetermined wave form, the other of said members supporting a plurality of capacity arms, each of said arms being relatively narrow in width with respect to its length, and means for relatively moving said capacity arms over said capacity island at a predetermined speed.

5. In amusical instrument as in claim 4 in which the distance between adjacent capacity arms is exactly equal to the length of said capacity island.

6. In a musical instrument as in claim 4 in which said capacity arms are surrounded by a grounded metallic shield.

7. In a musical instrument as in claim 4 in which saidcapacity island is surrounded by a grounded metallic shield.

8. In a musical instrument ducing sounds in which an alternating voltage is selectively impressed upon a sound producing means through a key, a pair of impedance branches having a center tap, said sound producing means being electrically connected between said center tap and ground, means for impressing an alternating potential across the imvariable condensers, means to vary for electrically propedance branches, means connecting the mid point of said alternating potential to ground, said center tap being connected to said impedance branches at a point at which no potential exists between it and ground, means for varying the impedance of one of said impedance branches and key operated means for actuating said impedance vai ing means.

9. A musical instrument as in claim 8'in which said impedance branches are made of a material whose impedance varies as a function of the voltage impressed on it and said means for varying the impedance includes key controlled means for impressingvoltage across the impedance branch whose impedance is to be varied.

10. In a musical instrument, means for generating a high frequency voltage of predeter mined frequency, a resonating circuit tuned to said predetermined frequency, a plurality of variable condensers, means to vary the capacities of said condensers in accordance with respective predetermined wave forms and at predetermined frequencies within the audible range, said condensers coupling the output of said high frequency voltage generator to said resonating circuit, output of said resonating circuit to obtain an electrical wave of predetermined characteristics, and means for converting said demodulated wave into an acoustic wave of predetermined pitch and timbre.

11. In a musical instrument, means for generating a high frequency voltage of predetermined frequency, a resonating circuit tuned to said predetermined high frequency, a plurality of the capacimeans for demodulating the.

ties of said condensers in accordance with respective predetermined wave forms and at respective predetermined frequencies within the audible range, .said condensers adapted to' couple the output of said high frequency voltage generator to said resonating circuit, means for selectively rendering respective variable condensers effective as coupling means, means for demodulating the output of said resonating circuit to obtain an electrical wave of predetermined characteristics, means for impressing a low frequency current upon said demodulated electrical wave to obtain a varying demodulated wave of predetermined characteristics, and means for converting said varying, demodulated wave into an acoustic wave having a predetermined pitch and timbre and a tremolo, the frequency of which is determined by low frequency current.

EARLE L. KENT. LE ROY C. PASLAY.

the frequency of said.

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