US1915861A - Method and apparatus for the production of music - Google Patents

Description

June 27, 1933;

c. T. JACOBS ammo];

AND APPARATUS FOR THE PRODUCTION OF MUSIC Original Filed Sept. 22, 1931 2- Sheets-Sheet, 1

IN V EN TOR.'- I

June 27, 1933.

c. JACOBS 1,915,861

METHOD AND APPARATUS FOR THE PRODUCTION OF MUSIC 4 Original Filed Sept. 22, 1931 2 Sheets-Sheet. 2

II I

TUBE 2! INKENTOR:- W

Patented June 27, 1933 UNITED STATES.

PATENT OFFICE.

CHARLES T. JACOBS, NEW PROV'l'DENGE TOWNSHIP, UNION COUNTY, NEW JERSEY, ASSIGNOR TO MIESSNER INVENTIONS, INC.,- A CORPORATION OF NEW JERSEY METHOD AND APPARATUS FOR THE PRODUCTION OF MUSIC Application filed September 22, 1931, Serial No. 564,305. Renewed November 17, 1932.

' mental frequency component but also one or more coincident higher frequency compo.- nents harmonically related to the fundamental. The fundamental and these higher frequency components may each be termed a partial of the composite vibration. Typical of such vibrators are, ofcourse, strings under. longitudinal tension; and strings are shown as the vibrators in the accompanying drawings. I do not wish to limit my invention to use with strings, however, it being adaptable for use with any other such tuned vibrator as above mentioned.

- In the. U. S. Patent 1,906,607, issued to me' -May 2, 1933, I pointed out that the oscillations produced by translation of the vibrations of the various points on a vibrating string were of different waveform; but that while an infinite number of such waveforms were available by such translation at different points, they did not represent as large as possible a variety of tone qualities. I

showed, however, that if oscillations produced by translation of the Vibrations of two or more string points were combined, new

tone qualities became available; and further, that if the several'oscillations were controllable before combination in respect of relative amplitudes and relative phases, an extremely wide variation in final waveform and harmonic structure, and hence tone quality, could be effected. Methods and apparatus were disclosed in that application for such multi-point translation, relative amplitude andphase control, and subsequent combination of oscillations. The present application issconcerned principally with extensions and modifications of the. means and methods therein disclosed, together with specific means and methods for producingmore particular types of .output tones.

Thus it is an object of my invention to provide improved means and methods for translating the vibrations of tuned vibrators into electric oscillations of a harmonic structure selectable within wide limits; andlikewise for selectively varying over a wide range the harmonic structure or waveform of electric oscillations produced by translation of the vibrations of tuned vibrators.

A further object is the provision in a musical instrument of the class described of improved vibration-oscillation means and methods suitable for producing almost any desired quality of tone; and likewise such means and methods for producing a quallty of tone selectively variable over a wide range. Y i

It is another object of myinvention to provide lmproved and convenient controls for effecting the variation and selection abovementioned; and more specific objects are the provision of means and methods for obtaining'from the vibrations of tuned Vibrators electric oscillations of various particular harmonic structures: e. g., containing only or predominately even or odd numbered electrical and electro-acoustic apparatus embodying my invention;

Figure 2 1s a partial plan view of the mechanical apparatus shown in Figure 1;

Figure 3 is a view similar-to Figure 2' butillustrating an alternative plan arrangement of the mechanical apparatus shown in Figure l; and

translating .partial components, containing substantial- Figure 4 is a further cross-sectional view of a string and its supports illustrating a particular arrangement of translating devices adapted to the production of practically pure fundamental frequency oscillations from string vibrations having appreciable upper partial components.

the latter, but it will be understood that any means or device for producing either sustained or decadent vibration of the string at its fundamental and at least one harmonic frequency may be substituted for hammer 8. A plan view of this apparatus showing a group of strings 1 of progressive lengths for vibration at progressive frequencies of the musical scale appears as Figure 2.

Below the several strings 1 will be seen, in both Figures 1 and 2, conductive strips 9, 10 and 11, preferably of small cross-section, and above the several strings similar conductive strips 12 and 13. These strips may conveniently be supported by somewhat flexible insulating strips 14, to which the conductive strips may be cemented, as is more fully disclosed in the co-pending application of Benjamin F. Miessner and .myself, Serial No. 558,207, filed August 20, 1931. The conductive strips will each be seen to be slightly spaced from each of the strings 1; and such spacing is in general preferably as small as possible without producing any contact betweenthe strips and any string 1 under conditions of maximum vibration of the latter. It will be appreciated, of course, that such spacing of a conductive strip will in general be greater, the nearer such strip to the center of the strings. While particular means of securing the insulating strips 14 have been disclosed in the joint co-pending' application abovementioned, it is suflicient for the purposes of this specification that they be. se-

cured in any convenient manner preserving the insulation aiforded by them to theseveral conductive strips 9, 10, 11, 12 and 13 affixed thereto.

The conductive strips may be electrically connected, through various switching arrangements comprising group of switches 15, group .16, and double pole double throw switch 17, hereinafter more fully discussed, to the grids of a plurality of vacuum-tubes shown in Figure 1 as 21, 22 and 23. .The cathodes or filaments of the tubes may be connected together and energized as by battery 24. A tap 25 on battery or other potential source 26 may rovide a source of anode current for thetu s. Between the cathodes'of the tubes and the'negative of battery 26 may be provided a condensively -by-passed resistor 27 for the biasing of the grid of each tube, throu h an associated high resistance 28, negative y with respect to its cathode. In

the output circuit of each tube may be connected the primary of a transformer, such electrical center of the associated tapped re-' sistor, such switch in each bank being designated as 54. The eletrical centers of the tapped resistors, and the common connection of each switch-bank, may be connected together as shown and to the potentiometer 29;

and the variable contact of this potentiome ter may be connected to the grid of a fourth vacuum tube 34. The cathode or filament of this tube may conveniently be paralleled with those of tubes 21, 22 and 23; and its anode current may be supplied from the tap 25 on battery 26. In the output circuit of this tube may be connected amplifier 35; and to the amplifier may be connected loudspeaker 36. Electrostatic shielding 37 may be disposed about the tubes 21, 22, 23 and 34 and their associated circuits, about the leads thereto from the conductive strips 9, 10, 11, 12 and 13, and around such strips. Such shielding may be connected to the positive terminal of battery or potential source 26 and also to capo 6 orto some othermember or members electrically connectedto strings 1,

' whereby the latter may be rendered at the potential of such positive terminal of battery or. source 26. It willbe' understood, of course, that tubes with unipotential cathodes suitably ener ized from alternating current may be substituted fortubes 21, 22, 23 and 34 and battery 24; likewise that a suitable rectifying, filtering and (voltage dividing.

system may replace battery or source 26, etc.

Consideration being given to the manner of functioning of the apparatus shown in Figure 1, it will be seen that between each strip 9, 10, 11, 12' and 13 and each string 1 a small electrostatic capacity exists; and that, with the switches in groups 15 and 16 open and switch 17 in the lefthand position. as shown, thetotal capacity formed between each one of the strips 9, 10, and 11 is in series with one of the resistors 28 and the battery 26. These capacities are therefore charged to the potential of battery 26. Upon vibra-' tion of any string 1 in a vertical plane, as'produced by impact therewith of hammer 8, the capacity between strip 9 and the re ion of such strin immediatel thereabove will vary oscillatori y, as'will l' ewise but in less degrce the total capacity between strip 9 and ages, in amplified form, respectively appear the strings. This oscillatory capacity variation, because of the fixed charge in the ca-- pacity, produces an'oscillatory variation of the voltage across the capacity. The frequency, waveform and harmonic structure of this voltage variation correspond respectively to the like characteristics of the vibration of the mean point of the vibrated string opposite strip 9; and such oscillatory voltage variation, or A. C. voltage, is applied to the grid of tube 21. Similarly an A. C. voltage corresponding in its characteristics to the vibration of the mean point of the vibrated string above strip 10 appears at the grid of tube 22; and a voltage corresponding to the vibration of the mean string point above strip 11 at the grid of tube 23. These voltacross the tapped resistors 41, 42- and 43, as will be understood.

If now there'be closed one switch of each bank, other for example than switch 54, there will be seen to beprovided a continuous circuit including aportion of each of the tapped resistors 41, 42 and 4:3, and including the potentioineter 29. Thus voltages appearing across the three tapped resistors may be made to appear in combination across potentiometer 29; and it will be seen that the absolute (and hence the relative) amplitudes, of these several voltages may be regulated, and that the absolute (and hence relative) phases thereof may be reversed at will, by

choice of the switch closed in each bank; Elimination from potentiometer 29 of volt age derived'from anyone or more of the tappedresistors may be effected by closing the switch 54 in the associated switch bank,

whether or not other switches in that bank be closed; or by closing two or more switches connected to taps on opposite sides of the electrical center of the resistance. Furthermore certain'amplitudes of voltage not available upon closing of any one switch in a bank may be obtained by closing two or more switches connected to taps on the same side associated switch open and the other maintaining it closed.

The composite voltage made 'to appear across potentiometer 29 may be thereby regulated in amplitude; and may thereafter be amplified by tube 34 and amplifier 35 and.

translated into sound'by loudspeaker 36.

The choice of position of the various conductive strips associated with the various strings determines to a large extent the types and range of tone qualities available from the system. In general, as might be expected from the segmental nature of the vibration of a string at its various harmonically related partialfrequencies, the nearer the center of the string a translating device be.

of the combining means-e. g., the switchbanks 51, 52 and 53that such cancellation can be effected; and in order that the fullest advantage be derived from the wide range of combining adjustments available in a given case, it is desirable that the oscillations produced by the combining adjustment which most accentuates the lower partials, be sufficiently rich in higher partials to make them ordinarily musically useful. Then the adjustments which 'mostelfectively cancel out the lower partials need not be invariably employed, instead being available for the production when desired of harmonic structures especially rich in higher partials. To this end I have in general found it desirable to employ translating devices relatively. near the extremities of the strings. Thus strips 9, 10 and 11 in Figures 1 and 2 are respectively shown at approximately 1/20, 1/12 and 1/8 of the length of each string forward from the rear end of the active vibratory portion thereof It is possible, however, to obtain a harmonic structure very rich in higher partials without positioning of translating device or system extremely near the extremities of the strings, and without special adjustments -of the combining controls. This may be accomplished by employing two translating devices or systems permanently or optionally connected together independently of the combining controls, and so arranged that'the lower partial components produced by each oppose each other'. Thus in Figuresl and 2 I show conductive strip 12 positioned at approximately 1/6. of the length of each string forward from the rear end of the active portion thereof, and group of switches 15,'by'one of which it may optionally be connected in parallel with strip 11,'which as above-mentioned is positioned at approximately 1/8 string length forward from the rear ends. It is important, with a capacitive translating device and for the purpose at may be effected without positioning on opposite sides of the string, as will be understood.

When strip 12 is parallel with strip 11, the combination yields oscillations equivalent, in relative weakness of the lower partials, to those produced by a' single strip much nearer the end-of the string than either of them.

. A special arrangement of translating devices very useful for the production of colorful tonal effects, for frequency doubling or for the more or lesscomplete elimination of even partials from oscillations and output tones, is the use of translating devices at least approximately similarly spaced from the two ends of the active vibratory portion of each string-i. e., symmetrical longitudinally about the center of thest'ring. Thus in Figtures 1 and 2 I show conductive strip 13 positioned at approximately 1/20'of string length back of the forward ends of the several strings 1,-a similar spacing to that of strip 9 from the rear ends. By setting the switch 17 in the right-hand position instead of the left-hand position as shown, it will be seen that strip 13 is substituted for strip 11, making active the three strips 9, 10 and 13. If now switch 54 of bank 52 be closed, so that strip 10 is inactive in contributing to the final oscillations, there remain active the symmetrically placed strips 9 and 13. If .the separate outputs from each of these two strips be adjusted to introducev into the circuit of potentiometer 29 similar amplitudes and aiding phase of the fundamental component, by

closing of appropriate switches in banks 51 and 53, the combined oscillations will be without even partials. If the similarity of amplitudes -ofthe separate oscillations be somewhat upset, the combined oscillations will have some even, but will predominate in odd, partials. Ifsimilarity of amplitude but opposition of fundamental phase be established by'theswitch-banks 51 a'nd53, the

combined oscillations will be without the original fundamental frequency or other odd partials, thus producing the octave of the string frequency. If the fundamental phase opposition be maintained butamplitude similarity somewhat upset, the combined oscillations will contain some odd, but will predominate in even, partials. Again, small or large amplitudes of oscillations in. either phase from strip 10 may be combined with the various combinations from strips 9 and 13; or with oscillations from strip 13 alone, in which latter case the resulting oscillations Will be characterized by incomplete tendencies toward even or odd partial predominance, the two strips 10 and 13 being in a most general sense but by no means exactly, symmetrically placed about the center of the string.

Asdong as strip 13 is to be used alone to supply oscillations to tube 23' and switchbank 53, it is of no significance whether it be placed above or below the strings 1. But in order that it may on occasion be combined in parallel with other strips by group of switches 16, and to the end that it may then serve in general to emphasize even partials rather than odd, it has been shown on the opposite side of the strings from the strips 9, 10 and 11. It may be noted that a strong tendency toward even partial predominance may at times give the musical effect of coincident playing of higher octaves-of the notes actually played.

Switches such as groups 15 and 16, which possible without considerably more complex.

apparatus. Thus, while more than three separate input tubes and switch-banks may be employed, the use of switches performing such functions as 15, 16 and/or 17 makes possible almost as wide harmonic structure control without such additional apparatus.

The number of separate input tubes may even be reduced to two without tremendous sacrifices of the flexibility of the system if suitable switches such as 15, 16 and 17 be employed. Switches in the groups 15 and 16 and double pole double throw switch 17, i

being each a two position switch, may convem'ently be controlled bv tabletsas abovementioned for the switches in the banks 51, 52 and 53.

For purposes .of simulation of the tone quality of particular instruments, or for any of several possible-reasons dictating a particular choice of tonal characteristics, a departure may at times be desirable from the effects produced by the sole action of any one ofthe translating systems (e. g., strips 9, 10, 11 etc.) or by the joint action of any two or more 'in any particular combination efl'ected as by the switch-banks. Thus, for

example, a particular translating syst m, or

combination of such systems with particular put oscillations therefrom before combinaamplitude and phase adjustments ofthe outa tone control isfactory in the middle musical register, but at the same time may provide oscillations in the bass register which contain too high relative amplitudes of lower partials. As a means of correcting this and similar difficulties, I show in the output circuit of tube 34 device 45, which may for example comprise an inductance 46, a capacity 47, and a resistance or potentiometer 48. W'ith the elements of the device arranged as shown, either the inductance or the capacity may be made effective to shunt the output of tube 34, by adjustment of the variable contact of the potentiometer toward that element. The potentiometer is preferably of four times, or more than four times, the lowest value of resistance which may be shunted across the output of this tube with negligible effect on efficiency. This permits asetting of the movable contact, i. e., at midposition electrically on the resistance of the potentiometer, such that negligible effect, when desired, is felt from the inclusion of the device in circuit. The choice of inductance and capacity values may readily be determined with the aid of principles well understood in the art of audio-frequency amplification, regard being had for particular results desired in a given case.

It will be understood, of course, that the more effective be the inductance as a shunt across the line, the greater will be the attenuati0n of lower partials of the bass tones produced by the system. On the other hand, the more effective be the capacity as a shunt,

' the greater will be the attenuation of the higher frequencies, particularly of the higher partials of the high treble tones. It will further be understood that the tone control device shown illustrative only, any of several well-known circuits and/or devices directed to similar ends being capable of substitution therefor.

Such tone control devices may further be employed, and I hereinafter claim as my invention their employment, to control one or more of the separate series of oscillations before combination thereof by the combining apparatus. Thus I have shown a similar tone control device 45 in the output of each of the three tubes 21, 22 and 23. In this position they may be made to produce a wide variety of effects; including that of an accentuation of either very low or very high frequencies, which is accomplished by attenuating that range of frequencies in one of two sets of oscillations derived from two translating devices or systems and being principally opposed against each other, at least as to their components in that range, by the phase ad uStment effected by the switch-banks or equivalent combining system.

When each translating system, e. g., strip 9, 10-, 11, etc., is positioned opposite a corresponding fractional-position of each string,

tends to be uniform in action with respect to the translation of particular partials of the vibration of each string. This condition may not always be desirable; and as a method of providing departure from such uniformity of particular partial translation characteristics in a rational manner, I have included illustrative Figure 3. Here the fractional distance of each strip 9,10, 11, 12 and 13 from the respectively nearer end of the string will be seen to be progressively less, the longer the string; but the ratios between themselves of the spacings of the several strips from such ends of each string have the whole system shown in Figure 2 being available to produce v these discriminating effects.

Occasionally it may be desired to produce for some musical purpose a practically pure tone; or, again, practically pure tones may be desired at some point in a musical instrument in which a desired harmonic structure is built up by synthetizing a group of harmonically related such tones. To obtain such a tone from a string or other mechanical vibrator vibrating with a complement of partial frequencies, I show in Figure 4 a special arrangement of translating devices. Thus three conductive strips 18, 19 and 20 may be provided, positioned at A,, and A-of -active string length respectively from the front end of the active portion of the string. These three strips may be electrically connected together and to the input of an electrical system similar to that shown in Figure 1- e. g., to thegrid to tube 21 in that figure. trips 18 and 20 must be similarly spaced from string 1, thus producing oscillations having a similar amplitude of fundamental component; and the spacing of strip 19 from string 1 may be adjusted until the amplitude of fundamental component produced by it is twice that produced by each of the other two devices. Under these conditions no 3rd, 5th, 11th, or 13th, partials will be present in the output oscillations; which condition will be found convenient as a test for proper position of strip 19. Due to the symmetry of strips 18 and 20 about the longitudinal center of the string, and to their aiding connection, they jointly translate no even partials; strip 19 being at string, where no even partial vibrationv takes place, consequently translates none; and the the same distance from the center of the.

3rd, 5th, 11th and 13th as abovementioned.

Consequently of the partia's up to and including the 14th, only the 7th and 9th are translated; and if string vibration 'at these partial frequencies be kept low by the exciting means, as by hammer 8 striking string 1 partial are eliminated at approximately 1/8 its active length back of the front end thereof, as is well understood in the iano art, the net upper partial content 'of the translated" oscillations will be very low. Furthermore for at least a limited range of simultaneously available musical notes, these upper partials may be reduced to a negligible value by means of the tone control device in the output of tube 21 and/or of tube 24. Tubes 22 and 23 and associated apparatus need not, of course, be employed in this embodiment of my invention.

It will be understood that while I have shown and described an electrostatic form of translating device or system, the principles of my invention are equally applicable to any other form .of translating device or system which may be associated with, and be actuated by the vibration of, particular portions of the vibrators. It will further be understood that while I have shown tapped resistors 41, 42 and 43, and banks of switches 51, 52 and 53, for controlling the amplitudes and phases of the separate series of oscillations before combinations, other forms of amplitude and phase controls such for example as tapped resistors and multipoint single-pole switches, or center-tapped Potentiometers, may be substituted therefor, or the variable controls entirely omitted when selective artlcular partial translation is not required, and the other features of my invention at the same time retained. It will finally be un-. derstood that the apparatus and circuits shown are capable of wide modification with- 'out departure in the combinations, or

methods of use, thereof from the spirit or scope of my invention, as hereinabove dis-.

closed and'in the appended claims defined.

I claim 1. In a musical instrument, the combination of a plurality of tuned vibrators; means for vibrating said vibrators; a plurality of mechanico-electric translating systems, each system being associated with a portion of each vibrator different from that with which each said 55 be other system is associated and ing arranged .to translate into a series of electric oscillations the vibrations of the therewith associated such portions; adjustable'meansindividually operative on at least one of said series of oscillations for altering the relative amplitudes of components thereof on an absolute frequency basis; and means following said adjustable means for combining the oscillations of the several such.

series.

2. In a 'muslcalmstrument, the combinetion-of a plurality of tuned vibrators;imeans for vibrating said vibrators; a plurality of mechanico-electric translating systems, each system being associated with a portion of 'each vibrator different from that with which each said other system is associated and being arranged to translate into a series of electric oscillation. the vibrations of the therewith associated such portions; selective means for varying the characteristics of the oscillations of the several such series relative to each other; adjustable means individually operative on at least one of said series of oscillations for'altering the relative amplitudes of components thereof on an absolute frequency basis; and means following said selective and adjustable means for combining the oscillations of the several such series.

3. In a musical instrument, the combination of a plurality of tuned vibrators; means for vibrating each of said vibrators; a plurality of systems each for translating into a series of electric oscillations the vibration of a difierent portion of each of said vibrators; a plurality of electric work circuits; means for applying the oscillations of each of-such series across a respective such work circuit to develop a voltage therein; a plurality of taps-on each said work circuit; and an electrical circuit, including a plurality of two-position switches individually connected to said taps, wherein voltages from said work circuits may be variously combined.

4. In a musical instrument, the combination of a tuned string; means for vibrating said string; two mechanico electric translating devices positioned on opposite sides of said string, respectively adjacent portions thereof having a slight longitudinal'separation, each for translating the vibration-of the adjacent said portion into a series of el ectric oscillations; and means for combining said two series of oscillations.

5. In a musical instrument, the combination of a tuned string; means for vibrating said string; two mechanico-electric trans lating devices. respectively adjacent two points on said string which divide the active length thereof-into three parts of which the outside two are substantially equal, eachpf said sys tems being arranged to translate into a series .of electric oscillations the vibration of the adjacent said point; and means for combinins! said two series of oscillations.

6. In a musical instrument, the combination of a tuned string; means for vibrating said string; two mechanico-electric translating devices, respectively adjacent two points on said string which divide the active length thereof into three arts of which the outside two are substantially equal, eachof said systems being arranged to translate into a setranslating device adjacent a point of said string distant by one-quarter of its active length from one end thereof and a mechanicoelectric translating device similarly adjacent I a point of saidstring distant by three-quarters of its active length from said end thereof, each of said translating devices being arranged to translate into a series of electric oscillations the vibration of the adjacent said point; a mechanico-electric translating device adjacent the central point of the active length of said string and arranged to translate the vibration of said central point into a series of electric oscillations having a .fundamental frequency component substantially double that of, each of said two first mentioned series; and means for combining said three series of oscillations additively with respect to'their fundamental frequency components.

8. The combination of a string; means for vibrating said string; a mechanico-electric translating device adjacent a point on said string distant by one-quarter of its active length from one end thereof and a mechanicoelectric translating device similarly adjacent a point of said string distant by three-quarters of its active length from said end thereof, each of said translating devices being arranged to translate into a series of electric oscillations the vibration of the adjacent said point; a mechanico-electric translating device positioned opposite the central point of theactive length of said string and arranged to translate the vibration of said central point into a series of electric oscillations having a fundamental frequency component substantially double that of each of said two first-mentioned series; means for combining said three series of oscillations additively with respect to their fundamental frequency components; and means for attenuating residual upper partial components from said combined oscillations.

9. In a musical instrument, the combination of a plurality of strings tuned to progressive fundamental frequencies; means for vibrating said strings; a mechanico-electric translating system associated with, and arranged to translate into a series of electric oscillations the vibration .of, a point on each string, the distances of said points from the ends of the respective strings having a progressive relation to the respective-lengths of said strings; at least one other mechanicoelectric translating system, each said other system being adjacent, and arranged to translate into a series of electric oscillationsthe vibration of, another point on each string, the distances of saidlast named points from the ends of the respective strings being a substantially constant multiple of the respective said first-mentioned distances; and means for combining said series of oscillations.

10; In a musical instrument, the combination of a plurality of tuned, electrically conductive vibrators; a plurality of electricallyconductive members, each said member being positioned adjacent a portion of each of said vibrators different from that to which each other said member is adjacent and forming electrical capacities with said portions; an electrical work circuit unilaterally connected to said vibrators; a source of D. (1.

means for connecting said conductive members selectively to said work circuit.--

11. In a musical instrument, the combination of a plurality of tuned "vibrators; means for vibrating said vibrators;'a plurality of electrical work circuits; a, number greater translating systems, each system being associated with a portion of each of said vibrators different from that with which each said other system is associated and being arranged to translate-into a series of electric oscillations the vibrations of the therewith associated said portions; and means interposed between said translating devices and said work circuits, and selective with respect both to said translating systems andto said work circuits, for applying to said work circuits said various series of oscillations.

12. The method of producing electric oscillations from a tuned vibrator and of regulating their harmonic structure, which consists in vibrating said vibrator at a plurality of its partial frequencies, in translating the vibrations of each of a plurality of por- "tions of said vibrator'into a series of electric oscillations, in attenuating components of the oscillations of one of said series in a degree varying with absolute frequency, and in thereafter combining theoscillations of the several such series.

13. The method of producing electric oscillations from a tuned vibrator and of regulating their harmonic structure, which consists in vibrating said vibrator at a plurality of its I partial frequencies, in translating the vibrations of each of a plurality of different portions of said vibrator into a series of elec-.

tric oscillations, in regulatin the characteristics of the oscillations of t e several such series relative to each other, in attenuating components of the oscillations of one of said series in a degree varying with absolute frequency, and in thereafter-combiningthe oscillations of the several. such series.

14. The method of producing electric oscillations in which alternately numbered par- ,potentialincluded in said work circuit; and p than said plurality of mechanico-electrictials predominate from a tuned string, which consists in vibratlng said string at a plurality of its partial frequencies, in translating intoa series of electric oscillations the vibration of each of two portions of said string substantially symmetrically located longitudinally about the center of the active length of said string, and in combining the oscillations of the two such series.

15. The method of producing electric oscillations from a tuned string and of varying their harmonic structure, which consists in vibrating said string at a plurality of its partial frequencies, in translating into a series of electric oscillations the vibration of each of two portions of-said string substantially symmetrically located longitudinally about the center of the active length of said string, in regulating the characteristics of the two such series relative to each other, and

in thereafter combining the oscillations of the two such series.

16. The method of generating electric oscillations of substantially pure fundamental frequency from a timed string, vibrating at its fundamental and other of its partial frequencies, which consists in translating into a series of electric oscillations the vibration of a point on said string distant by one quarter of the active length of said string from one .end thereof, in translatinginto a series of electric oscillations of similar funda: mental component amplitude the vibration of a point on said string distant by three quarters of the active length of said string from said end thereof, in translating into a series of electric oscillations having a fundamental component twice that of each of said two first;mentioned series the vibration of the central point of the active length of said string, and in combining said series of oscillations additively with respect to their fundamental components.

17. The method of generating electric oscillations ofsubstantially pure fundamental frequency from a tuned string vibrating at its fundamental and other of its partial frequencies, which consists in translating into a series of electric oscillations the vibration of a point on said string distant by one quarcomponents, and in attenuating residual up per partial components of said combined oscillations.

CHARLES T. JACOBS.

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