US2233058A - Apparatus for the production of music - Google Patents

Description

Feb. 25, 1941. ss 2,233,058

APPARATUS FOR THE PRODUCTION OF MUSIC Filed Kay 17, 1938 5 Sheets-Sheet 1 Feb. 25, 1941.

B. F. MIESSNER 2,233,058

APPARATUS FOR THE PRODUCTION'OF MUSIC Filed may 17, 1938 3 Sheets-Sheet 2 Feb. 25, 1941. sN 2,233,058

APPARATUS FOR THE PRODUCTION OF MUSIC Filed May 17, 1938 3 Sheets-Sheet 3 AMI. 7054:72'.

HI'IR Patented Feb 25, 1941 PATENT OFFICE 2,233,058 APPARATUS FOR THE PRODUCTION OF MUSIC Benjamin F. Miessner, Millburn,

Miessner Inventions, Inc.,

N. .L, assignor to I Mlllburn Township,

Essex County, N. J., a corporation of New Jersey Application May 17, 1938, Serial No. 208,357

19 Claims.

This invention relates to the production of music, and more particularly to such production from the vibrations of tuned vibrators through the medium of mechanico-electro-acoustic translation. The invention has especial reference to vibrators which are excited by impulse, such for example as struck or plucked strings or the like. An important object of the invention is the provision of improved arrangements whereby there may be produced from so-excited vibrators tones which are free of the influence of the excitati0n-for example, which are characterized by a smooth, rather than an abrupt, initial rise of am- J plitude, or inception.

Such arrangements are broadly known, having for example been disclosed in U. S. Patents Nos. 1,915,859 and 1,915,860, issued June 2'7, 1933, and No. 2,071,649 issued February 23 1937, all to Miessner et al., showing such arrangements espe cially as applied to pianos. In certain of the disclosed arrangements a tone could not be prolonged after the release of the key whose depression produced it. In certain other of those arrangements a tone could be prolonged after key release by the holding down of the sustaining pedal of the piano; but if the key were re-depressed before the sustaining pedal was released, the tone produced by the re-depression would be characterized by the typical pianistic, rather than a smooth inception. It is an object of this invention to provide arrangements of the character described which permit the tone to be prolonged by an auxiliary means such as a piano sustaining pedal, but which provide the smooth tone inception upon any re-depression of a key even though the sustaining pedal may not in the meantime have been released.

It is an object of the invention to provide novel and advantageous means for varying the efficiency of the mechanico-electric translation in an instrument of the class described.

It is an object to provide such varying means capable of very rapid operation without the production of objectionable clicks or other transient effects in the output tone.

It is an object to provide improved forms and dispositions of switching means particularly adapted for the efficiency variations abovementioned.

Other and allied objects will more fully appear from the following description and the appended claims.

In the description reference is had to the accompanying drawings, of which:

Figure 1 is a partial vertical cross-sectional view of a piano wherein my invention has been embodied in simple form;

Figure 2 is a partial horizontal cross-sectional view of a pianowherein the embodiment of Fig- 6 ure 1 is slightly elaborated;

Figure 3 is a partial view of the nature of Figure 1 but illustrating the embodiment of my invention in modified form;

Figure 4 is a partial view of the nature of Fig- 10 ure 1 but illustrating the embodiment of my invention in further modified form; and

Figure 5 is a partial view of the nature of Figure 1 but illustrating the embodiment of my invention in still further modified form.

According to a preferred embodiment of the instant invention, the action of translation of electric oscillations and sound from the vibrator, or the efficiency of the mechanico-electro-acoustic translating device or devices associated with the vibrator, is momentarily reduced to at least substantially zero at the instant of excitation of the. vibrator. While this may be done by suitable control of a polarizing or sensitizing voltage, or equivalent, for the translating device, by arrangements of the nature of those shown in one or more of the patents abovementioned, I have found it difficult to effect satisfactorily, and without objectionable clicks or the like, a thoroughly sufficient reduction of the sensitizing voltage in the minute interval between the beginning of key depression and the resulting excitation of the vibrator. I have found, however, that if the momentary reduction under discussion be efiected in the signal or oscillation-output circuit of the translating device, it may be eifected both with the necessary rapidity and with a substantial absence of clicks or other transient disturbances, and without difliculty. v

In an instrument of the piano type I have found a very satisfactory way of carrying out this operation to be by suitable means associated with the hammer, and thereby rendered operative during the interval of the closest approach of the hammer to and its contact with the string; and for a disclosure of a simple embodiment of my invention, operating in this manner, reference is invited to Figure 1. Herein there are illustrated'suilicient of the parts of a grand piano of the electronic typei. e., operating by mechanico-electro-acoustic translation-clearly to show the association of my invention therewith.

A typical piano metallic 'frame or plate is shown as I, having front portion la, capo bar lb,

and rear portion lc, these portions appearing in cross-section. Secured underneath the front plate portion In isv a wrest-plank}, in which are retained tuning pins 3 passing upwardly through the suitably apertured front plate portion la. From each tuning pin, under the capo or plate portion lb, and over a bridge l to a respective hitch pin 0 in the rear plate portion I0, is strung a respective string 1. Any number of strings per note may of course be employed; but it may be assumed for purposcsof description that the two strings 1 shown in Figure 1 comprise a pair of strings for one note of the instrument. The bridge 4 over which the strings are strung is preferably supported for vertical vibration, as to a plurality of vibratile ribs 5 terminally secured to relatively rigid portions of the instrument.

The strings for each note are excitable by an individual hammer 8, having a tail 9, and a shank I 0 pivoted to a stationary flange H. For operating each hammer there is provided a respective pivoted key l2, operatively connected to the hammer through the usual piano action mechanism l3 interposed between the intermediate rear portion of the key I: and the hammer shank ill. Near the rear end of the key is secured the upwardly extending back-check ll. Since the parts described in this paragraph are conventional, it will be understood that upon depression of the key (1. e., of its forward extremity) the associated hammer I will be propelled against and caused to strike the associated strings I, immediately rebounding therefrom; and that, unless the key depression be of an extreme "staccato" nature, the hammer tail 9 upon the rebound will be driven into contact with and will frictionally engage the then-raised backcheck ll, the hammer being held by this engagement in a partially raised position until key release.

Normally resting on the strings of each note and damping the same is an individual damper it. Each damper is carried at the top end of a respective rod it, which passes downwardly through an apertured guide rail ll to a respective bushing |8,-this bushing being pivoted to a respective flange l9 whose rear extremity is in turn pivoted to a suitable stationary member. The forward end of each damper flange is very slightly spaced above the rear extremity of the respective key, so that it and the damper will be raised upon and during depression of that key.

Pedals of the conventional sustaining" and sostenuto types are schematically shown as 20 and 24, respectively, pivoted as at It and 25. To the rear pedal extremities are pivotally secured the respective rods 22 and II, each rod being raised by depression of the respective pedal. The sustaining pedal rod 22 is pivotally connected at its top extremity to a horizontal rail 23 which passes underneath all the damper flanges is, to raise all of them, and all the dampers from the strings, upon and throughout depression of the pedal 20. The sostenuto pedal rod 26 is pivotally connected at its top to a strip 21, which along its rear edge is hinged to a stationary portion, and which extends from that edge forwardly and downwardly toward the damper bushings ll; depression of the sostenuto pedal 24 accordingly rocks the strip 21 clockwise (when viewed a illustrated). Rearwardly from each damper bushing 18 extends a small lug 28 which, if its respective key is depressed, will be raised into the arcuate path of the forward edge of the strip 21;- accordingly when the sostenuto pedal 14 is depressed while any key is depressed, the lug ll associated with that key will be engaged and held in an upward position, and the associated damper thus of! the associated strings, throughout the continuance of the sostenuto pedal de pression. It will be understood that quite simpliiled pedal arrangements have been shown. wholly however in the interest of simplicity of illustration.

For translating into electric oscillations the vibrations of the strings of the pair illustrated in Figure 1, I have shown an electromagnetic translating device or pick-up 30 having its pole in spaced relation to the strings; this is desirably mounted to the vibratile bridge support, or ribs 5. The output leads 3| from the device II (in which may for example be serially connected the translating devices 30a for other notes) may be led to a control potentiometer 32; and oscillations translated from string vibration by the device 30 (and devices 30a) and impressed across the potentiometer 32, may from the potentiometer be applied to the input of a cascade schematically illustrated as comprising amplifier 31, control system 34, further amplifier 35, and loudspeaker or other electro-acoustic translating device 36. It will be understood that these oscillations are amplified by 33 and 15', may be controlled in such respects as volume, bass and treble predominance, and the like by 34; and are translated into sound by 38.

In Figure 1 the control means for effecting the translation reduction concomitant with vibrator excitation comprises essentially a switch shunted immediately across the translating device 30, and closed by the hammer when that is in contact with the strings. To avoid clicks," however, the switch is preferably not of simple abrupt-opening and -closing variety, but rather of a variable impedance form; also preferably, the normal or open impedance of the switch is finite, though high (i. ,e., several times the output impedance of the translating device 30 at the higher audio frequencies) While the switch or variable impedance device may be constructed in any of a variety of ways, I have illustrated it in Figure 1 as comprising a resistance element ll formed on the under side of a horizontal metal strip 40 parallel with and a little below the strings 1 above the damper guide rail IT; a sprin 42 preferably touching the bottom of the resistance element at the rear element extremity, and curving forwardly and downwardly therefrom to have its own forward extremity slightly overhanging the front edge of the rail I1; and an arm 43 extending from the rear surface of the hammer 8 opposite the shank l0, upwardly and rearwardly to have its rear extremity in a position normally spaced below the forward spring extremity, and preferably carrying a lug 44 of insulating material on top of its rear extremity. The spring 42 may be secured at its rear extremity on top of an insulating rail 45 which extends upwardly from a shelf 48 of insulating material disposed on top of the damper guide rail l1 behind the damper rod l6. Above the rear spring extremity may be provided an insulating spacer 41, and the rear extremity of the strip it may be secured against the top of this spacer. The strip 40 and spring 42 form the electrical terminals of the switch or variable impedance device, and have been shown connected immediately across the translating device II by the leads 3!.

The resistance element ll extends, on the unthe hammer will carry der side of strip 40, forwardly from adjacent the spacer 41; it may be of any suitable material, such as carbon or graphite. Preferably it is arranged so that the resistance it provides between spring 42 and strip 40 is very high when the spring 42 touches (as it preferably normally does) only the rear extremity of its bottom surface, and so that that resistance decreases logarithmically or according to some other taper as the spring 42 is warped up into contact with more and more forward portions of that surface. To indicate such tapering, which it will be undertsood may be effected by suitable arrangement of one or more of the characteristics of material and thickness and area and the like of the element, I have illustrated the element as of forwardly diminishing thickness.

It will be understood that normally the high resistance between 40 and 42 provides a negligible shunt on the translating device 30. When,

however, the key I2 is depressed and the hammer 8 is propelled upwardly to strike the strings, with it the arm 43 and lug 44; and when the hammer has risen partially toward the strings the lug 44 will engage the forward extremity of the spring 42, the further rise of the hammer warping the spring upwardly into contact with more and more forward portions of the bottom surface of the resistance element 4|. Preferably the spacings are such that at the instant the hammer strikes the strings the resistance between spring 42 and strip 40 will be at substantially zero or negligible value -e. g., the

' tially raised position wherein its spring will be in contact with substantially the entire bottom surface of the resistance element. As the hammer rebounds from the strings the spring 42 will of course fly downwardly from the resistance element; and preferably the spacings are also such that hammer rebound to the partail 9 is engaged by the back-check 4 will be sufficient to effect the restoration of the spring 42 to its normal position. Thus the efficiency'of the translating device 30 (i. e., its ability to deliver stringvibration-representing oscillations to the potentiometer 32) is being reduced in the latter portion of the approach of the hammer to the strings; is substantially zero at the instant of striking of the strings by the hammer; and is immediately raised thereafter-at a rapid, but nevertheless finite, rate determined of course by the rate of rebound and the tapering of the resistance element ll Accordingly there is produced by the mechanico-electro-acoustlc transiating system a tone from which the influence of the impulse excitation is. removed. and whose inception is smooth rather than Wholly abrupt.

The efilciency of the translating device, restored to normal upon hammer rebound from the strings, is thereafter unaffected when the key is released; and so long as the strings are permitted to continue the vibrations caused by the striking (i. e., so long as the damper i is maintained raised from the strings) the translating device will continue efficiently to translate their vibrations, and the output tone will continue in correspondence with those vibrations. This action is clearly independent of whether the damper 5 is held raised by continued key depression or by depression of either of the pedals 20 and 24. It will further be observed that if, while the damper I5 is being held raised by either of the pedals to permit continuance of the string vibration and output tone, the key I2 is re-depressed to cause another striking of the strings,

the efficiency of the translating device 30 will be varied downwardly and upwardly in an identical manner to that already described; Just before the striking oi the strings the previous tone will be cut out at a rapid but finite rate, and immediately after the striking the new tone thereby occasioned will come in with a smooth inception. The variation of the translation efficiency in a sufficiently rapid manner for these actions, and yet without objectionable "clicks" or other transient disturbances, appears to be greatly facilitated by the fact that there is being varied no large sensitizing voltage or the like, but only the inherently small signal'voltage.

It will of course be understood that an individual strip 40, resistance element 4| and spring 42 may be employed for each note of the instrument. Each spring 42 is preferably of very light material and of very light downward bias, so that it will occasion only a negligible alteration of the required "touch on the respective key I2. Each strip 40 may if desired be of light and springy material, in which case the spacings of the components will of course be adjusted to take into account a yielding oi the strip as the respective spring 42 is warped up into contact with the respective resistance element 4|; however, each strip 40 is arranged to remain quite stationary, and this may be insured if desired by a plate 48 of insulating material secured immediately above the strips 40.

It may frequently be desired to play the instrument without eliminating the influence of the impulse excitation on the output tones. For this purpose the operation of the switches or variable impedance devices may be readily suspended by a displacement of their entire assembly rearwardly by a small distance, to obviate the engagement of the springs 42 by the hammer lugs 44. Accordingly the shelf 46 has been shown as held on top of the rail I! by means of screws 50 passing through forwardly elongated slots 49 in the shelf, these slots permitting the rearward displacement abovementioned. A means for moving the shelf has been schematically illustrated as a vertical lever 5| having its top extremity pivotally attached to the bottom of the shelf, intermediately pivoted to a stationary standard 52, and having the forwardly extending horimntal rod 53 pivotally attached to its bottom extremity. The rod 53 may pass slldably through a hanger 54 to terminate in a knob 55 accessible to the player; by pulling forwardly on this knob he may move the shelf vrearwardly, and vice versa, to selectively place the variable impedance devices out of and in operation.

While only a single translating device per note has been illustrated in Figure 1, it will be understood that the disclosed arrangements are capable of employment in instruments wherein a plurality of such devices are employed at different longitudinal positions along the strings for each note, as for tone quality variation purposes as disclosed in U. S. Patent No. 1,906,607 to Jacobs; I have illustrated a typical such employment in Figure 2. This is a partial horizontal sectional view of an instrument, otherwise similar to that of Figure 1, wherein there are included for each note a plurality of switches or variable resistance devices per note, for a corresponding plurality of translating devices per note; the line A--A of Figure 1 indicates the plane of the instrument corresponding to that on which Figure 2 is taken.

In the instrument of Figure 2 two translating devices, 29 and 30, are provided at difierent longipreferably,

tudinal positions along the strings for each note. The devices 88 are connected in series and across potentiometer 82'. while the devices 28 are connected in series and across potentiometer 82"; and these potentiometers may have fixed intermediate contacts connected together, and variable contacts connected to the input of amplipliiler 88, so that the oscillations from the devices 88 and those from the devices 28 may be mixed together in any of a variety of phase and amplitude relationships for tone quality control in well known manner.

There are again provided as many metal strips and associated resistance elements, designated respectively as 48' and H, as there are notes, but the strips and elements are centered below the spaces between the string groups for the several notes rather than immediately under those string groups; and two mutually distinct narrow springs-a righthand spring 42 and a leithand spring 42"-are provided below each resistance element 4|. The righthand spring 42 for each element 4| and the lefthand spring 42" for the next element to the right are both adapted to be engaged by the single lug 44 of the hammer which strikes the string group straddled by those two elements; thus two switches or variable resistance devices per note are provided. Every other one of the strips 48' is electrically connected to every other one of the electrical junctions between successive translating devices 28; and the springs 42 and 42" associated with each one of those strips are respectively connected to the junctions (between devices 29) immediately to the right and to the left of that junction to which that strip is connected. The intervening strips 40' are respectively connected to every other one of the junctions between successive translating devices 38; and the springs 42? and 42" associated with each one of those strips are respectively connected to the junctions (between devices immediately to the right and to the left of that junction to which that strip is connected. To simplify the drawing, these connections have been indicated in Figure 2 by the numbering of the inter-device junctions, and the partial showing of conductors from the strips and springs numbered correspondingly to the junctions to which those conductors are respectively to be connected. It will be understood that the manner of functioning of the instrument of Figure 2 is entirely similar to that already described in connection with Figure 1, excepting only that the striking of a string group by its hammer entails the momentary substantial shorting of each of the plurality of translating devices associated with that string group, rather than of only a single device associated with the group. It will further be understood that any of a variety of arrangements of the several strips, resistance elements and springs may be employed, the particularly illustrated arrangement being typical only.

In the instruments of Figures 1 and 2 each switch or variable impedance device has operated to short out the respective translating device during excitation of the associated strings; it will be understood, however, that the switch or equivalent device may otherwise act upon the translating device. Thus in Figure 3 I show an arrangement wherein the switch or equivalent device opens the signal circuit from the translating device to the cascade of potentiometer 32, etc. In this figure the translating device for the strings of one note has been schematically shown, by way of example, as a pressure-responsive device 80 7 this is compressed between the top of the bridge 4' (which is at an appropriately lowered level. and supports the device 88) and a triangular member II (on top of the device 88) over which the strings are strung and against which they bear. Typically the device 88 may be a piezo-electric translating device. One or the output terminals of each device 88 may be connected to groundi. e., established at a reference potential. The other output terminal or each device It may be connected, as by a respective conductor II, to the top extremity of potentiometer II-the bottom extr'emity or the potentiometer being shown connected to ground, and the amplifier 88 being connected from ground across a variable portion or the potentiometer.

In the conductor 8| for each note there is serially included a respective switch which is normally closed, but which is opened by the hammer during the brief interval of its proximity to and contact with the strings. It has been illustrated as comprising a small compressible conductive element resting on top of a small metal strip 84 which is positioned on the shelf 48 above mentioned in connection with Figure l; and an effectively pivoted metallic lever 88 normally resting on top of the element 85 and extending there from forwardly .to overhang the front edge of the guide rail H, to be raised out of contact with the element 85 by the hammer lug 44 during the mentioned brie! interval. The lever 88 may be effectively pivoted at its rear extremity by being there secured .to the front of a short leaf spring 81, which in turn is secured on .top of the insulating rail 45 abovementioned in connection with Figure 1; spring 81 and metal strip 84 form the switch terminals which are serially interposed in conductor 8|. The compressible conductive element 85 may be one whose resistance varies to at least some extent with its compression; purely typically, it may be a pad of felt or similar material, rendered conductive by impregnation with a colloidal graphite emulsion or the like. Both gravity and spring 81 may normally bias the lever 88 downwardly to compress the element 85, so that a moderate resistance only is normally present in conductor 8|. When the lever 88 is raised by the hammer lug 44 the element 85 expands somewhat and its resistance smoothly increases to a relatively high value, before the lever actually leaves the element to fully open-circuit the conductor 8i; conversely as the lever 88 returns to normal position (after string-striking) the conductor 8| is close-circuited with a relatively high serial resistance value, which thereafter smooth- -ly decreases to the normal value as the element 85 re-compresses. This resistance variation in the switch is readily made sufficient .to substantially obviate clicks and other undesirable transients.

It will be understood that the lever 88 will rest against the element 85 at all times except during the brief interval immediately preceding, at, and immediately following the striking of the string by the hammer-i. e., the interval dur ing which the translating device of earlier fig ures was shorted, or in process of being shorted Thus effects are produced on the translation eificiency broadly similar (to those described above It will further be understood that the action 01 the switches may be eliminated when desired by a movement of shelf 48 as above described, thl means for moving the shelf having been irac tion-ally illustrated in Figure 3.

Even when the conductor BI is open-circuitei by .the lever 88 there may be a residual smal it will .be understood capaci-tative transfer of oscillations between the lever and the element 85, slightly impairing the perfection of the open-circuiting. To suppress such transfer the lever 86 may, as the hammer most closely approaches and touches the string, be closed and momentarily pressed against the bottom surface 01 a compressible conductive element 88 (which may be common for all notes) whose top surface is secured to the bottom of a grounded metal plate 89 extending forwardly from the top of the insulating spacer 41 provided above the insulating rail 45 as in Figure 1. Thus the translating device is not only open-circuited from slightly before to slightly after the string-striking instant, but is also short-circuited at that instant; its electrical output is thus positively diverted irom the signal circuit to an inactive circuit at the critical instant.

In Figure 4 I illustrate a typical application of my invention to use with electrostatic mechanicaelectric translating means. In this figure all the strings I are grounded, as by the grounding of the rear plate portion to. Spaced underneath the strings for each one note is disposed an electrode 90, which may .be in the form of the head of a conductive screw; this screw may for example pass downwardly through and be supported by a forward extension 4a of bridge 4, as described and claimed in my co-pending application Serial No. 187,646, filed January 29, 1938, on which Patent No. 2,200,718 has since been issued). The screw or electrode 90 is connected through a respective high resistance 9| and a common high resistance 92 to a source 93 of sensitizing potential, which is in turn connected to ground. To illustrate the connection in circuit of the electrode for another note, I have shown a resistance 9| therefor, connected analogously to 9| for the illustrated note.

It the source 93 be a high voltage D.'C. source, that it will efifect a charge in the string-to-electrode capacity; and that oscillatory variations in the capacity, produced by string vibration, will vary the voltage across the capacity and the voltages across the resistances BI and 92, since the latter prevent abrupt changes of the charge. If the source 93 be a source of oscillations of super-audible frequency, it will be understood that it will produce a current flow through .the string-to-electrode capacity, which will be modulated by the oscillatory variation in the capacity, to produce modulated voltages across the resistances 9| and 92. In either event the oscillatory components of the volt-age across the common resistance 92 may be applied through a condenser 94 to the potentiometer 32 (the amplifier 39 being operated to demodulate, as well as to amplify, when the super-andible-oscillation' source is employed).

To carry out my invention in the instrument of Figure 4 I may connect, from each electrode 90 to ground, a capacity which is normally of negligible value, but which is momentarily greatly increased when the hammer strikes the string. This I have illustrated by the employment of shelf 96, insulating rail 45, insulating spacer 11, and springs 92 as in Figure 1-but with each spring adapted to be raised into close adjacency with a respective small metal plate 95 secured, above the more forward spring portion, to the bottom of a common insulating plate 99 extending forwardly from the top of the spacer 9?. Each plate 95 may be connected to a respective electrode 90, while all the springs 42 may be connected to ground. To obviate shorting of each spring 42 against its respective plate 95 when it is warpedv up thereagainst by the hammer lug 44, a thin mica or other dielectric sheet 9'! may be secured against the bottom of each plate 95.

As the hammer approaches the string and the spring 42 is warped upwardly, the capacity of the spring to the respective plate 95 is increased, to have a maximum value when the hammer strikes the string; its value may then be many times that of the associated string-to-electrode capacity, so that it then heavily loads, or largely shorts, the string-to-electrode capacity. This operates greatly to reduce the string-vibrationfrequency oscillations (or modulations) in the voltages across resistances SI and 92, because the capacity in series with those resistances is being oscillatorily varied in greatly reduced degree (i. e., the total such capacity has been great- I; raised, with no increase in the variable component of the capacity).

When the source 93 is a D. C. source there is the further action of a momentary reduction of the volt-age across the string-to-electrode capacity, since its charge is suddenly largely transferred to the capacity plate 95, and time is required for re-charge through resistances 9| and 92; this D. 0. Voltage reduction will be understood to have a reducing eflect on the translation efliciency. This additional action may beeliminated if the connection of the springs 42 be transferred from ground to the ungrounded terminal of source 93- i. e., to coincide with the connection of resistance 92 to the source-thus providing a reduction of the degree of elimination of impulse excitation components from the tone. I have accordingly shown a potentiometer 98 shunted across the source 93, and the springs 42 connected to a variable contact 99 on this potentiometer; by this contact their potential may be progressively varied between the terminal potentials of that source. "A still further reduction of the impulse component elimination may be effected it, with the contact 99 at the non-ground extremity of the potentiometer and source, the connection of the resistance 92 to the source be varied away from that non-ground extremity; accordingly I have shown the resistance 92 connected to a variable contact I00 on the potentiometer, which is intended to be fully variable over the potentiometer independently of the position of the contact 99. By more extreme adjustments of the last-mentioned character it is in many cases possible to reverse the eifectsof the system, to provide an actual accentuation of the impulse excitation components of the output tones.

It will of course be understood that the mechanical control means, for moving the shelf 46 to remove the springs 42 from and to restore them to the paths of the hammer lugs 44, may still be employed, having been fractionally illustrated in Figure 4.

In Figure 5 I illustrate the application of my invention to an instrument wherein a plurality of electrodes 90, 90a and 9019 are employed for the strings of each note. All the strings may be grounded, as in Figure 4; and a sensitizing voltage source 93 is provided, also as in Figure 4, but it may be shunted by a potentiometer i0l having a grounded center-tap I02 and having three independently variable contacts I03, M311 and With. The electrode 90 is connected through a respective high resistance M to the contact I03, the electrode 99a through a respective high between spring 42 andresistance BIa to the contact WM, and the electrode 90b through a respective high resistance 0Ib to the contact I03b. Resistances 9|, Ma and 9Ib' for the electrodes associated with the strings for an adjacent note have been illustrated to indicate their manner of connection in circuit. For the three illustrated electrodes of each note there may be provided a single respective resistance I04, of high value and with one extremity grounded, and these electrodes may be connected to the non-ground extremity of resistance I04 through respective condensers I05, I05a and I051). It will be understood that the system as so described will produce across resistance I04 oscillations of the fundamental frequency of the respective note (or oscillations modulated at that fundamental frequency, ac cording to the nature of the source 93), the harmonic development of the oscillations (or modulations) being determined by the joint adjustment of the variable contacts B00, will). In carrying out the main aspects of my invention with the system of Figure ii, I may ior e iple treat each resistance iil l in general as o translating devices Bil of Figure 3; l1 ac cordingly shown a respective conduct tilt;

forming a signalv circuit from the resistancetilt to non-ground extremity of potentiom 3 2, and in this conductor I have serially interposed an appropriate switch operated by the hammer. Similarly to the switch of Figure 3, this may be made of double-throw variety, whereby to switch the resistance lll 'l from a normal con nection with the potentiometer 3?; to a connection with ground.

In Figure 5 I have shown each switch of a capacitative form wherein the compressible conductive elements 05 and 00 are employed in arrangement and connection like those of Figure 3, but with a member therebetween movable to form a capacity alternately with the one and with, the other element. This member may be a spring I01 electrically connected to the resistance I04, and extending forwardly from between rail 05 and spacer 41 to between the elements and 08; on the top and bottom of the spring opposite those elements are secured thin mica or other dielectric sheets I00, which prevent actual contact of the spring with either element. To the forward extremity of the spring may be secured the Bakelite or other insulating extension I09, which overhangs the guide rail I! to be engaged by the hammer lug 44. To prevent minute electrostatic eii'ects-upon contact of the lug 44 with the extension I09, a small metallic plate IIO may be secured underneath the forward extremity of the extension I09, and grounded as by flexible conductor III.

Normally the spring I01 rests through the lower dielectric sheet I08 on the element 85, compressing the latter and providing a capacity thereto which completes the circuit of conductor I06. Operation of the hammer will of course move the spring I01 upwardly to interrupt this circuit, and to bring the upper dielectric sheet I00 into momentary compressingcontact with the bottom of the element 88; this provides momentarily a capacity between spring I01 and the element 08 through which the voltage from resistance IN is transferred to ground. In a switch of this cha acter the abruptness of the switch action is tempered both by the capacity variation with spring movement and by the resistance variation with the element compression. This compression also provides a beneficial resillent mechanical stop action for the spring movement-it being understood ofcourse that the parts will be adjusted to avoid this compression noticeably interfering with the normal hammer movement. In the instrument of Figure 5 the 5 mechanical control means for moving the shelf 40 has again been fractionally illustrated, for purposes apparent from preceding description. While in the several figures I have disclosed certain particular combinations of various i translating devices with various forms switching means or equivalents, it will be undw stood that these particular combinations intended to be illustrative rather than exhaustive, and that the elements may be widely intcr-- iii changedsubject only to such broad qualiilcatlons as that the capacitative switching me is are bestadapted for high-impedance translating devices, and the like. And generally I inteno no unnecessary limitations by virtue oi i tails of the disclosure, which obvious Y 1 widely varied without departure from ,c ii-r of the invention. In. many oi? the appended claims I undertake to express the scope of the invention broadly, subject however to ch I proper limitations as the state oi the art may impose.

I claim:

1. In a musical instrument having a tuned Vi," brator: the combination of impulse excl at! means for said vibrator; a signal channel: means for eiiecting a translation of vibratic of said vibrator into corresponding electric cillations in said channel; and variable imped ance means, electrically connected withir said it signal channel and operatedby said cxcltl 5:: means, for varying the efficiency of ti'fti'l;-llation.

2. In a musical instrument having a tuned string: the combination of a hammer movable to strike said string; a signal channel; meam for effecting a translation of vibrations of aid string into corresponding electric oscillations in said channel; and variable impedance means, electrically connected within said signal ch nel and operated by said hammer, for varylnz. the efflciency of said translation,

3. In a musical instrument having a tuned vibrator: the combination of a hammer in able to strike said vibrator; means for effectin" a translation of vibrations of said vibrator in electric oscillations; and switch means, a ciated with said hammer in position for Ftl subjected to operation thereby only when t. same is in close adjacency to said vibrator, or m varying the efilciency of said translation.

4. In a musical instrument having a tuner: vibrator: the combination of impulse excitinr; meansl for said vibrator; a signal channeli means for effecting a translation of vibrations of said vibrator into corresponding electric o1- cillations in said channel; and variable-limped ance means, operated by said exciting means for substantially shorting said channel.

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thereof; means normally applying said oscillations to said amplifying circuit; an inactive vibrator: the combination of circuit; and means, operated by said exciting means, for diverting said oscillations from said amplifying circuit to said inactive circuit.

'7. In a musical instrument having a tuned impulse exciting means for said vibrator; ai signal channem; means for effecting a translation of vibrations of said vibrator into electric oscillations in said channel; and switch means, connected within said signal channel, for varying the efliciency of said translation when said exciting means is operated.

8. In a musical instrument having a tuned vibrator: the combination of impulse exciting means for said vibrator; a signal channel; means for effecting a. translation of vibrations of said vibrator into electric oscillations in said channel; and variable-impedance means, connected within said signal channel, for varying the efliciency of said translation when said exciting means is operated.

9. In a musical instrument having a tuned vibrator: the combination of impulse exciting means for said vibrator; a signal channel; means for eifecting a translation of vibrations of said vibrator into electric oscillations in said channel; and. variable-capacity means, connected within said signal channel, for varying the efliciency of said translation when said exciting means is operated.

10, In a musical instrument having a tuned vibrator: the combination of impulse exciting means for said vibrator; means for efiecting a translation of vibrations of said vibrator into electric oscillations; switch means for varying the efiiciency of said translation, disposable to be operated by said exciting means; and means, mechanically associated with said switch means, for moving the same to suspend the operation thereof by said exciting means.

11. In a musical instrument having a tuned vibrator: the combination of a hammer movable to strike said vibrator; means for effecting a translation of vibrations of said vibrator into electric oscillations; a lug secured to said hammer; switch means, having a movable element disposable in the path of said lug,'for varying the emciency of said translation; and means for moving said switch means relative to said hammer to carry said movable element out of the path of said lug.

12. In a musical instrument having a tuned vibrator: the combination of impulse exciting means for said vibrator; high-impedance means for efiecting a translation of vibrations of said vibrator into electric oscillations; high-resistance means in series with said translating means; and variable-capacity means shunting said translating means and varied by said exciting means.

13. In a musical instrument having a tuned vibrator: the combination of impulse exciting means for said vibrator; an electrode forming a capacity with and varied by vibration of said vibrator; high-resistance means for charging said capacity; and variable-capacity means shunting said first-mentioned capacity and varied by said exciting means.

14. In a musical instrument having a tuned vibrator: the combination of impulse exciting means for said vibrator; a signal circuit; means for effecting a translation of vibrations of said vibrator into 'electric oscillations in said circuit; and means, connected in said circuit and comprising a compressible conductive element and a member movable into and out of compression against the same, for varying the efliciency of said translation when said exciting means is operated.

15. In a musical instrument having a. tuned vibrator: the combination of impulse exciting means for said vibrator; a signal circuit; means for effecting a translation of vibrations of said vibrator into electric oscillations in said circuit; and means for varying the efficiency of said translation, comprising a compressible conductive element, a member movable into and out of compression against the same, and thin dielectric means interposed between said element'and said member.

16. In a musical instrument having a tuned vibrator: the combination of a member arranged for movement to contact and excite said vibrator; a key depressible to cause said member movement; means for eifecting a translation of vibrations of said vibrator into electric oscillations; and variable-impedance means, operated by said member upon depression of said key and free of operative influence by said key upon subsequent release thereof for momentarily varying the emciency of said translation.

17. In a musical instrument having a vibrator and a system for the mechanico-electro-acoustic translation of its vibrations: impulse exciting means for said vibrator, and variable-capacity means responsive to said exciting means for varying the eiilciency of said translation.

18. In a musical instrument having a vibrator and a system for the mechanico-electro-acoustic translation of its vibrations: a hammer movable to strike said vibrator, and variable-capacity means operatively associated with said hammer for varying the efliciency of said translation.

19. In a musical instrument having a vibrator and a system for the mechanica-electro-acoustic translation of its vibrations: impulse exciting means for said vibrator, an oscillation-transmitting channel in said translating system, and means serially interposed in said channel and responsive to said exciting means for varying the efiiciency of said translation.

BENJAMIN F. NHESSNER.

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