US3077137A

US3077137A - Electrical pick-up for a reed musical instrument

Info

Publication number: US3077137A
Application number: US851364A
Authority: US
Inventors: Benjamin F Miessner
Original assignee: Wurlitzer Co
Current assignee: Wurlitzer Co
Priority date: 1951-11-08
Filing date: 1959-11-06
Publication date: 1963-02-12
Anticipated expiration: 1980-02-12

Description

1963 B. F. MIESSNER 4 3, ,1

ELECTRICAL PICK-UP FOR A REED MUSICAL INSTRUMENT Original Filed Nov. 8. 1951 2 Sheets-Sheet l l i I BENJAMIN E M/ESSNEI? IN V EN TOR.

ATTORNEYS Feb. 12, 1963 B F MIESSNER 3,077,137

ELECTRIdAUPICK-UP FOR A REED MUSICAL INSTRUMENT Original Filed Nov. 8. 1951 2 Sheets-Sheet 2 S E REED r0 PICK- UP 7 0 REED VIBRATION b BENJAMIN E M/ESS/VER INVENTOR.

ATTORNEYS United State This invention relates to percussive or other impulsively-excited vibrator instruments and more particularly to such instruments utilizing small beam type vibrators in combination with electronic translating apparatus for producing audible tones from such vibrators.

In electronic musical instruments, of the class contemplated by this invention, the beam type vibrators may be of the free-free, fixed-fixed, fixed-free or supported type. However, in the present invention, I prefer to use fixedfree type vibrators in the form of small reeds together with novel reed-clamping arrangements and novel translating devices whereby the instrument will produce tones characteristic of a conventional tensioned string-piano. Once having provided an arrangement for the production of piano tones, which have a low damping rate, I include novel means whereby the damping rate, or rates, of the tones can be altered at will to produce tones characteristic of other conventional instruments such as, for example, the harpsichord, harp, banjo, etc. The particular type of reed excitation means employed will depend, primarily, upon the character of the tones to be produced and although I prefer to use manually-operated or key-boardoperated hammer strikers or direct finger-plucking, mechanical or electro-magnetic plucking or normally-deflected and release type of excitation means may be used.

I prefer to use capacitive types of pick-ups acting as amplitude and/or frequency modulators of a radio frequency oscillator with appropriate demodulating, audio frequency amplifying and electro-acoustic reproducing devices.

The principal object of this invention is the production of piano-like tones from fixed-free vibratory reeds while maintaining the conventional piano-like performance and playing technique.

Since the tone of a tensioned-string piano normally has a low damping rate, or long time decay, it is essential that an electronic piano include such characteristics if the tonal qualities are to be acceptable. To date it has not been possible to duplicate such piano tone-damping characteristics when utilizing small vibratory reeds as the tone generators. This has been due, essentially to the fact that small vibratory reeds, with conventional mounting means, have a significantly higher damping rate than a tensioned string. While it is possible to utilize amplitude-controllable and phase-reversible, electrical feed back circuits of the regenerative or degenerative types for the control of the oscillation damping rates of vibratory reeds, I have found a simple way to decrease the normal damping rate of a small fixed-free reed whereby its vibration time equals or exceeds that of a tensioned string.

The musical tones of conventional instruments of the percussive or impulse excited class are differentiated chiefly by harmonic (or inharmonic) tone content, the damping rate of the tone as a whole, the damping rate of the individual partials of the tone, and, to some lesser extent, by the accompanying noise resulting from the particular manner of exciting the tone producer into vibration. In most instruments the noise resulting from the excitation means are non-musical and should be eliminated unless their traditional acceptance demands their inclusion.

atent O 3,077,137 Patented Feb. 12, 1963 In the present invention I provide any desired type of damped musical tone by an arrangement that includes suitable fixed-free vibrators, suitable impulse excitation means, suitable adjustable, and continuously-acting dampers for the vibrations of the vibrators and a suitable mechanico-electro-acoustic means for translating the vi brator vibrations into audible tones. By this I mean that the various components are of such construction and inter-related assembly that the desired type of damped musical tones are made possible by the control of the partial tone content of the individual vibratory reeds and by selective control of the reeds vibration damping rate.

This application is a division of my co-pending application Serial No. 255,383 filed November 8, 1951, now Patent No. 2,919,616. These improvements herein claimed consist chiefly in:

(1) The mounting support for the vibratory reeds and pick-ups;

(2) The provision of novel, individual pick-ups and suitable adjustments to eliminate certain undesired modes of reed vibrations from the translating apparatus and to provide desired adjustments of tone quality and amplitude.

An object of this invention is the provision of a single support for both the vibratory reeds and the associated pick-ups designed to eliminate capacity changes in the reed-pick-up assembly except such changes as are due to actual reed vibrations.

Another object of this invention is the provision of a support for the vibratory reeds and associated pick-ups which support is of novel construction to minimize the absorbtion of energy from vibrating reeds.

Another object of this invention is the provision of a novel pick-up for translating vibrations of a reed.

The above and other objects and advantages of the invention will become apparent from the following description when taken with the accompanying drawings illustrating various embodiments of the invention. It will be understood the drawings are for purposes of illustration and are not to be construed as defining the scope or limits of the invention, reference being bad for the latter purpose to the appended claims.

In the drawings wherein like reference characters denote like parts in the several views:

FIG. 1 is an isometric view of a reed secured to a reed support and intended to show the various different vibration modes of the support in response to normal vibration of the reed:

FIG. 2 is a top view of my reed base with three vibratory reeds and their associated pick-ups secured thereto;

FIG. 3 is a front view of the device shown in FIG. 2;

FIG. 4 is a cross-sectional view taken along the line A-A of FIG. 2;

FIG. 5 is an isometric view of the pick-up that is stamped from sheet stock;

FIG. 6 is similar to FIG. 5 and showing the opposed ends of the pick-up offset with respect to the body section;

FIG. 7 is a simplified side View generally similar to FIG. 4 but showing the pick-up ends disposed in the plane of the adjacent reed and centered outwardly of a nodal point of the reed;

FIG. 8 is a view similar to FIG. 7 but showing the pick-up modified to aline the pick-up ends with the nodal point referred to in the description of FIG. 7;

FIG. 9 is a view similar to FIG. 7 but showing another modification of the pick-up;

FIG. 10 is a set of curves showing the character of capacity variations, with reed vibrations, for the pick-up arrangement shown in FIG. 9;

FIGS. 11 and 12 are front views of a reed and pick-up and showing different spacings between the reed and pick-up ends to effect a change in translating efficiency;

FIG. 13 is similar to FIG. 11 and illustrates a means 3 for proper alinement of the pick-up, with respect to the reed, by use of a suitable tool;

FIG. 14 is similar to FIG. 11 and shows the relation ship between the reed and the pick-up for a minimum output tone damping rate; I

FIG. 14a is similar to FIG. 14 but shows the relationship between the reed and pick-up for a maximum output tone-damping rate; and a FIG. 15 is an isometric view illustrating two vibration modes of a fixed-free reed cantilevering from a support base.

When a vibratile reed is securely attached at right angles to the axis of a long support, the reed, when vibrating, tends to develop a like-frequency vibration in the support either by forced or resonant action. If the action is forced, the supports amplitude of vibration may be small, assuming the support to have a relatively large mass and stiffness. If the action is resonant, the vibra- 'tion amplitude of the support will be relatively much larger. Since the energy for vibration of the support is supplied by the vibrating mechanically-coupled reed, the reed loses this energywith a resulting diminution of its own vibration amplitude. If the support be made of a viscous or visco-elastic material having a large coefficient of internal viscosity at the reed vibration frequency and if the coupling between the reed and its support be large, the support will draw energy from the reed at a rapid rate especially if the energy transfer is a resonant action. The first requirement, therefor, for minimizing the reed energy losses due to the support is to make that support of a material having a low coeflicient of vibrational viscosi'ty. Such materials are cast bell alloys (such as 13 parts copper and 4 parts tin), glass, porcelain, high carbon steel of about 'Roc'kwell C 50 hardness, hard grades of cast brass, bronze or aluminum.

Additionally, the form of the support, or supports, carrying the reeds and the associated pick-ups should for eertain types of output tone, be such that there be no change in capacity between the reed and the pick-up except that due to reed vibrations. Therefore, the support must be stilt and non-vibratile. 'In the case of an electronic piano the number of reeds and pick-ups may number 7-0-88. Should these pick-ups vibrate, with respect to the reeds at a given small amplitude and in phase with each other, the translated output vibration would be 70-88 "times that of a single reed vibrating at the same amplitude. This pick-up support vibration could therefore, produce a very powerful foreign and undesirable frequenc component in the output tone of the instrument. To eliminate, or reduce as far as possible, such undesirable capacity variations between the reeds and the pick-ups Iprefer to mount the reeds and pick-ups on a common, massive and stiff support which itself is designed to absorb a minimum amount of energy from the vibrating reeds.

In order to explain the various modes of vibration imparted to 'a support by a vibrating reed we will assume, for purposes of analysis, a long, more or less rectangular bar. Reference is made to FIG. 1 showing a vibratory reed 10 having one end firmly secured to such relatively long bar 11. Normally, the reed is excited in such manner that it vibrates in a plane perpendicular to the axis of the support and as indicated by the arrows XX. In a straight, fixed-free reed, of uniform section, so vibrated, the frequency relationship between the fundamental vibration (partial I) and the other inherent vibration partials i as follows.

At each of the above frequencies the reed develops several types of forces in the bar 11, said forces tending to vibrate the bar at these same frequencies. These various vibration modes of the bar are discussed separately, below:

(a) Torsional vibration moden-The vibrations of the reed tend to vibrate the bar about the latters longitudinal axis YY. If the reed be located at one end of the bar, as shown, that portion of the bar to the right of the reed tends to remain at rest due to its own rotational moment of inertia. However, that portion of the bar adjacent to the reed tends to twist about the arc a-a having a radius r. Now, if any one of the bars own torsional vibration frequencies is equal to any of the reeds vibration partials, the bars torsional vibration frequency will be relatively large assuming that the vibrational Q of the bar is high.

(b) Lateral vibration m0de.-As the reed vibrates up and down it tends to lift the reed-attached side (front end) of the bar so that the bar tends to vibrate along the arc b-b having a radius W. If the rear edge of the bar is anchored to some other massive support the frequency of this particular vibration mode will be proportional to the bars thickness and inversely proportional to the square of the bars width. Obviously, this mode of vibration will have very much higher vibration frequencies than the torsional vibration mode.

(c) Longitudinall vibration m0de.--As the reed vibrates up and down it also tends to lift and depress the reed-supporting side of the bar so as to deform the bars axis. This sets up a longitudinal vibration of the bar and about its partial frequency nodal points as indicated by the are 0-6. This mode of bar vibration, like that of the torsional mode, is also obviously of much lower frequency than the lateral mode. 7

The only complete solution to the problem of eliminating the above-described vibrations of the reed-supporting member, and the resulting withdrawal of energy from the reed, is to make the supporting member so massive that the coupling of the reed to the support is insignificantly low, and so stiff that the lowest partial frequency of its three vibration modes is well above that of the highest partial frequency of the highest pitched, attached reed. While only the fundamental vibration frequency of each reed is desired for tonal output use in my piano, it must be remembered that higher vibration partials of the reed can cause increased damping of the fundamental component by resonant losses in the reed support.

Since a sutficiently massive reed support, to meet these ideal conditions, is impractically large and heavy, the compromise solution liesin making the reed forces, acting on the support (of practical size), as small as possible, other factors being equal. With given reed and base sizes, the reed to base coupling-can be lowered either by making the base stiffer and more massive or by reducing the size of the reed so that its vibratory forces which tend to deform the base are materially reduced. Since the stiffness of a cantilever beam'is proportional to the square of its thickness, the base-deforming vibratory forces of the reed can be reduced to A by halving the reed thickness. By experiment, and with due consideration given to other factors involved such as the reeds own self-damping rate and dimensional factors affecting translation of the reed vibrations, I have found the ideal reed thickness to be (9.025 to 0.035 inch, for piano tone production.

The lateral vibration mode of the reed-supporting base can be removed, conveniently, by making the width and thickness of the support sufficient short and large, respectively, so that the frequency of vibration is higher than the highest pitched reed, namely 4,092 cycles per second. Such support, or base, for the reeds and the pick-ups will now be described.

Reference is now made to FIGURES 2 and 3 which area top and front view, respectively, of my reed base 15 carrying the vibratory reeds 1'6, 16' and 16" and the pickups 17, i7, 17', associated with each reed. It will be understood the reed base 15 carries the full complement of tuned reeds and pick-ups which, in the case of a piano, may number 88. The reed base is made in one solid piece, preferably a metal casting, as cast metals have a microstructure having an inherently low vibration viscosity. By so making the reed base in a single casting, the structure is not subject to relative vibrations of the type possible in a multi-rnember support such as, for example, an assembly comprising a separate reed rail, a pick-up rail and an interconnecting plate. The reeds are individually clamped in position by large-diameter, fine thread,

sockethead set screws

18, 18', 18 each having a novel reedclamping end as shown in FIG. 4. The end of the screw 18 is concave resulting in a small circumferential ridge 20 that engages the upper surface of the reed 16. A similar screw 21 has its ridge 22 axially alined with the ridge 2th of the screw 18, and engages the opposite surface of the reed. It may here be stated the circumferential ridges in the clamping screws are very small in height, in the order of 1 mil. Since the set screws are made of hardened steel such ridges bite into the reed surface thereby defining a very sharp, positive reed termination having certain outstanding advantages. As shown in FIGS. 3 and 4, the reed base 15 is provided with a series of

transverse holes

25, 25, 25" having diameters larger than the width of the reed passing therethrough. These holes serve two purposes, namely, as a clearance area to permit unimpeded vibration of the reed and to permit a firm clamping of the reed solely by the opposed set screws to maintain a sharplydefined reed-termination point.

The reed base 15 has a progressively-varying Width, indicated by the letter W in FIG. 2, said width being a maximum at the bass or low-frequency reed end and a minimum at the treble or high-frequency reed end. In actual practice the width of the base at any point is approximately 75% of the axial length of the proximate reed, as will later be explained. The spacing of the reed bass from the reed and the angle 0 are such as to permit free and unrestricted reed vibration at its maximum desired amplitude.

The front face of the base is square with the top surface and approximately /2 inch thick. A series of holes is bored into the front face of the base such holes being parallel to the reed and directly above them. The

tubular bushings

26, 26, 26 are force fitted or otherwise attached into these holes, said bushings being made of an insulating material, such as a plastic. The bushings have internallythreaded sections to accommodate the

screws

27, 27, 27" by which the conductive pick-

ups

17, 17, 17" are secured in proper position such that the associated reeds may vibrate freely between the opposed pick-up ends 28, 28', 28".

As shown in FIG. 5, the individual pick-up 17 is punched from a sheet of suitable metal having a thickness such that the pick-up is non-vibratile per se. I have found soft brass suitable for this purpose. As shown in FIG. 6, the ends 28 of the pick-up are bent at a right angle to the body section so that when the pick-up is secured in position on the reed base these ends will be in a plane substantially parallel to that of the associated reed, as shown in FIG. 4. These ends straddle the associated reed forming a dual capacity pick-up and the transverse center line of the pickup ends 28 is made to coincide with the nodal point of the reeds vibration partial 11. Such nodal point is located approximately 0.22L from the reeds free end (L being the effective axial length of the reeds vibratory portion) as is well known in this art and as is indicated in FIG. 4. With the pick-up so positioned, vibration partial II of the reed is not translated into a capacity change between the reed and the pick-up and, therefore, such vibration partial is eliminated from the output tone of the instrument. The longitudinal notch 30 in the body of the pick-up permits adjustment of the pick-up up and down with respect to the reed. Such adjustment controls the relative effect of the reeds fundamental and partial vibrations in the output tone. If the ends 28 of the pick-up are positioned in a plane high above or below that of the reed when the reed is in the at rest position, essentially only the fundamental vibration appears in the output tone at reed vibration amplitudes not exceeding the normal transverse spacing between the reed and the pick-up ends. If the ends 28 of the pick-up are directly opposite the reed edges, that is, in the plane of the reed, the reed vibrations will be trans lated at double the frequency and the fundamental will disappear. In the latter case, the reed flies by the pickup ends at maximum velocity in its cycle of vibration so that the capacity peaks are highest and steepest generating, for maximum reed amplitude, the strongest complement of integrally-related partial tone vibrations.

Inasmuch as the individual pick-ups are insulated from each other and the reed base, the pick-ups may be provided with integral extensions 31 serving as terminals by which all pick-ups can be connected together.

In the assembly shown in FIG. 4, the plane of the outer end of the bushing 26 can be established with a high degree of precision such that when the pick-up 17 is secured thereto, by the fastening screw 27, the ends 28 of the pick-up will straddle the reed at the point representing the nodal point of the reeds partial II. In the event further adjustments of the pick-ups are necessary to align the pick-up ends with such nodal point this can be done by making the length of the bushing 26 somewhat shorter than required and then interposing a washer of suitable thickness between the bushing end and the pick-up. As a practical matter, the simple assembly illustrated in FIG. 4 is quite satisfactory for establishing the pick-up ends in proper position with respect to the nodal point of reed vibration partial II and further, critical adjustments can be made bending the pick-up as will now be described with reference to FIGS. 7 and 8.

FIGS. 7 and 8 are fragmentary side views similar to the cross-sectional view of FIG. 4. In FIG. 7 the pickup is shown extending straight down from the supporting bushing 26 with the pick-up ends 28 lying in the plane of the reed 16 when the latter is at rest. The precise nodal point for partial II of the reed is indicated by the line N positioned a distance 0.22L from the free end of the reed. It will be noted that the line N is displaced from the transverse center line of the pick-up ends 28, the latter being indicated by the line M. To establish an exact alinement of the lines M and N the body of the pick-up can be bent toward the fixed end of the reed as illustrated on an exaggerated scale in FIG. 8. In such case the pick-up ends 28 are bent upward slightly so that they again lie in the plane of the reed, as shown.

As has been stated above, a maximum, sharply peaked change in capacity between the reed and the pick-up occurs when the parallel ends of the pick-up lie in the plane of the reed when the latter is in the at rest position. However, my novel pick-up construction affords a simple means for altering the character of the capacity changes upon reed vibration. For example, the ends 28 of the pick-up can be bent out of parallelism with the reed surface as shown in FIG. 9. In such arrangement the time during which the reed is adjacent to the pickup ends is increased, and the maximum capacity between the reed and pick-up is decreased. However, the time during which the capacity remains constant within one cycle of reed vibration is increased to a significantly larger value resulting in a substantially flat-topped capacity variation curve as shown in FIG. 10. Such capacity curve results in a change of tone quality and it will be apparent that other tonal qualities can be obtained by other adjustments of one or both pick-up ends relative to the reed. Furthermore, since reed vibration amplitudes which are within the confines of the adjacent pick-up arms 28, produce no variation of reed to pick-up capacity. This capacity will be modulated only when the reed vibration amplitude exceeds these confines as indicated by the arrows aa. Thus a strongly excited reed, with maximum amplitude as indicated by the arrows 19-49, will be translated only until its amplitude falls slightly below amplitude aa, and this results in an increase of output tone damping rate. This applies of course only when the lower and upper ends of the pick-ups are equidistant from the reed in its at rest position. If, for example, the pick-up is raised so that its lower (bent) edge is in the plane of the top surface of the reed, then minimum damping of the output tone may be secured but with the retention of the tone quality changes produced by the bent arms.

The translation efiiciency of my pick-up is also adjustable by merely bending the pick-up ends closer together or further apart as shown in FIGS. 11 and 12 which are front views of the pick-up and reed. In FIG. 11, the spacing between the reed 16 and the ends 28 of the pick-up is relatively small whereas the similar spacing in FIG. 12 is relatively large. Both illustrations are drawn to an exaggerated scale for purposes of illustration as the spacing between the inwardly-facing ends of the pick-up is, normally, about 0.005 inch greater than the width of the associated reed, thereby providing a normal clearance gap of about 0.0025 inch on either side of the reed. While the spacing between the pickup ends can be established, in the first instance, during the punchingoperation by which the pick-ups are made, a precise spacing can be set by bending the legs of the pick-ups inwardly or outwardly in conjunction with a suitable gauge. Once the spacing between the pick-up ends is set the pick-up can be adjusted angularly about its fastening screw to equalize the two clearance, or air, gaps between the reed and the adjacent pick-up ends. A suitable tool may be employed for this operation. As shown in FIG. 13, the tool comprises a solid, rectangular rod section 35 having a pair of flat air gap spacers 36 secured thereto to form a fork. Each of the spacers has a thickness corresponding to the clearance to be es tablished between the sides of the reed 16 and the ends 28 of the pick-up 17. These spacer members are inserted into the clearance gaps, as shown, after which the pick-up clamping screw 27 is tightened. Several such tools may be used each having parallel spacer members of a given thickness, such as .00 .0025", .00 etc., to provide different pick-up sensitivities.

The damping of the output tone of the reed may also be controlled by the vertical positioning of the pick-ups relative to the associated reeds. The lowest such damping rate prevails when there is a small amount of overlap between the adjacent faces of the reed and pick-up ends as shown in FIG. 14. Here the slightest residual tremor of reed vibration causes a variable-area type of change in the capacity between the reed and the pick-up. The highest tone damping rate prevails when the ends of the pick-up are positioned relatively far below or above the reed, the latter arrangement being illustrated in FIG. l4.a, where the length of the arrows a-a indicate the maximum amplitude of reed vibration.

The individual reeds of the instrument can be set into vibration in numerous ways. If we assume, for the present, that the reeds are to be impulsively-actuated, as when struck by a hammer, I have found that the reed should be struck at a point OlZSL to 0.35L from its fixed end (L being the length of the vibratory section of the reed) by a moderately soft hammer. The .35L point is the nodal point for vibration partial IV and the .25L point is the nodal point for partial V. Thus, if a reed be struck precisely at one such point the corresponding vibration partial of the reed is not excited and, therefore, does not appear .in the output tone of the instrument. However, if a relatively soft hammer is used and has a reed engaging face sufliciently large to span two or more vibration partial nodal points, the partials having such spanned nodal points will be only weakly excited. Additionally such hammer damps out such partials to a much greater extent than lower numbered partials. For

Partial No I II III IV V Partial frequency 627 1, 765 3, 440 I 5, 690 Vibration Cycles During Hammer Contact Time 10 62.7 175. 5 344 569 Obviously, since the hammer acts as a damper during its reed-contact time, it will extract, from the reed, a minute amount of energy during each cycle of its vibration and the total amount of such energy extracted will increase in proportion to the total number of such vibrations. If, therefore, a given small amount of damping effect for vibration partial I is represented by the damping factor then vibration partial II, which executes 6.27 times the number of oscillations of partial I, will be damped 6.27 times more than partial I. Partial III will experience 17.55 times the damping effect of partial 1, partial IV, 34.4 times that of partial 1, partial V, 56.9 times that of partial I, etc. These values assume that the hammer contacts the reed at equally-effective positions with respect to the individual nodal points for the concerned partials. In addition to the above, the specific initial vibration amplitudes of the individual vibration partials vary as their frequency so that the higher numbered partials drop out much faster than the lower. The point which I wish to stress here is that a proper choice of the hammer material and selection of its reed-contact points will, effectively eliminate, or render unimportant, the higher numbered partials of the reed with respect to the output tones of the instrument.

Vibration partial II of the reed, however, is the worst offender as to raggedness of initial tone quality because, if the pick-up be located at the reed tip this partial has an amplitude of the order of /6 that of partial I and is only 6.27 times higher in frequency. The advantage of positioning the pick-up at the nodal point for vibration partial II of the reed to thereby eliminate the partial II completely from the output tone is, therefore, quite apparent. In fact, such specific positioning of the pick-up permits the use of small reeds whose second partial II is not retuned from normal dissonance to harmony with partial I. Specifically, the normal ratio of the vibration frequencies of partial II to partial I of a clamped-free reed is 6.27, obviously a dissonant relationship. In addition, the positioning of the pick-up at the nodal point .for the reeds vibration partial II, as herein disclosed, also permits the use of hard, sharp hammers for excitation of the reed. Such hammer excitation of the reed generates a partial II vibration of normally high amplitude and provides little or no selective damping among the various reed vibration partials. Since my pick-ups do not translate partial II vibrations such dissonant partial does not appear in the pick-up translated output tone of the instrument. Minimizing of the relative amplitude of partial II is however preferable (as by soft hammers, .etc.), in conjunction with the partial II nodal point pick-up, to insure total absence of partial II from the output tone.

Reference is now made to FIG. 15 with respect to the following discussion describing another advantage of my novel pick-up construction. When the reed 16 is struck normal to its fiat side it will vibrate predominantly in the plane indicated by the arrows a-a, generally referred to as the A vibration mode. If, however, the reed be struck at an angle other than normal to its flat side the reed will also vibrate in the direction of the arrows bb, generally referred to as the B vibration mode. These two vibration modes are perpendicular to each other and the partial frequencies of one mode will not be consonant with those of the other mode unless the width dimension of the reed be very exactly predetermined in relation to its thickness. For example, if the reed has a Width exactly twice its thickness the vibration partials of the B mode will be exactly two (2) times the frequency of the corresponding partials of the A mode, a consonant relationship. While such reed dimensions can, of course, desirably be provided, such design limitation increases the cost of the reeds when the musical instrument comprises 88 tuned reeds to provide a pitch range of the piano. Therefore, it is preferable that the B vibration mode of the reed be eliminated from the translating apparatus. Normally, the striking hammer is designed to strike the reed normal to its flat side so that there is little or no vibration of thereed in the B mode. More importantly, a slight and undesirable B mode vibration of the reed is neutralized by the dual nature of my pick-up, as can be seen from FIG. 11 wherein a sidewise motion of the reed 16 produces no change in capacity between the reed and the pick-up as a whole. Obviously, an excessive B mode vibration of the reed may result in physical contact between the reed and one or the other of the pick-up ends thereby ruining the output tone. However, such condition does not arise in practice as the striking hammer and its operating mechanism can be designed for normal reed excitation in the A vibration mode and as the reed width is chosen to be several times its thickness thereby giving the reed a much higher stiffness in the B mode direction, this stiffness being proportional to the square of the width.

It will be noted the body portion of my pick-up lies in a plane normal to the reed axis whereby the mechanical coupling of the reed to the pick-up body is zero except for extremely large excursions of the reed. This is an important feature of the pick-up construction and orientation since the pick-up, loaded as it is by the pick-up ends, will have a natural, fundamental frequency well within the upper reaches of the reed scale of frequencies. Thus, with other than zero coupling the pick-ups, unless quite thick, could resonantly absorb some of the vibrational energy of the higher-pitched reeds and such pick-up vibration would also be translated through modulation of the reed to pick-up capacity. The relatively short and thick ends of the pick-up have a natural frequency lying beyond that of the highest reed and, therefore, are not a disturbing factor. Similarly, the insulating, tubular bushings that support the pick-ups are individually loaded by the pick-up and clamping screw and have a natural frequency beyond the range of the highest pitched reed and, therefore, can do no harm.

From what has been described thus far it is clear that I have taken steps to eliminate or neutralize all unwanted vibrations of the individual parts and the assembly thereof. The lateral mode of vibration of the reed base varies from the bass end of the instrument (where the reed base is of maximum width) to the treble and (where the reed base is of minimum width) so that at any reed position the natural vibration frequency of such reed-base-vibration mode is 8 or more octaves above the reed frequency. If the natural vibration frequency of the bass end of the reed base is of the same order, relative to the proximate reeds, as that of the treble end of the bass the intervening distance of several feet (in the case of a piano) is sullicient to decouple such vibrations.

The reed base may have suitabe longitudinal curvatures from one (bass) to the other (treble) for the purpose of effecting a straight hammer-striking line along the entire complement of reeds to simplify the installation of the numerous hammers. Where a sturdy, that is, massive and stiff, cabinet is employed to house the assembly of reeds and pick-ups the reed base may be screwed securely to the top, bottom or side of such cabinet, depending upon 10 the type of hammer action employed. This will further stiffen the reed base and increase its inertance against vibrational deformation and reed-energy losses.

Referring back now, the instrument assembly shown in FIGS. 1-4, inclusive, is designed primarily for hammer excitation of the individual reeds, such hammers being keyboard controlled as in a conventional piano. Such playing-key hammer mechanisms are well known and, since they form no part of my present invention, there is no need for a detailed showing thereof in this application.

Having now described the numerous novel features of my invention and various structural embodiments incorporating such features, as well as several novel instrument assemblies, numerous other variations and modifications of the individual components and their interrelated assembly will suggest themselves to those skilled in this art. Such variations and modifications can be made without departing from the spirit and scope of the invention as set forth in the following claims.

The invention is claimed as follows:

1. In an electric piano the combination of a plurality of elongated substantially flat reeds, reed support means supporting each of said reeds at one end thereof so that the reed cantilevers freely away from the support means therefor, each of said reeds having two longitudinal edges and defining on opposite sides of the reed two generally fiat longitudinal side surfaces, each reed being shaped to have a thickness perpendicularly to said reed side surfaces which is limited to only a small fraction of the width of the reed to constrict free vibration of the reed to a vibratory path generally perpendicular to said side surfaces of the reed, means for impulsively exciting each of said reeds for vibration, a generally fiat capacitive pickup element disposed alongside one longitudinal edge of each reed in generally parallel relation to the at rest position of the reed, each of said pickup elements having a thickness exceeding the thickness of the adjacent reed and defining a pickup surface extending along the adjacent longitudinal edge of the adjacent reed in electrically capacitive relation thereto and in a position disposed beyond the reed laterally in a direction generally parallel to said side surfaces of the reed, each of said pickup elements and the adjacent reed being positioned in relation to each other so that one edge of said pickup surface on the pickup element is substantially flush with a plane containing one longitudinal side surface of the reed when the reed is in its at rest position and the pickup surface and reed are disposed generally on opposite sides of said plane, and electric sound producing means connected to said pickup elements and said reeds to respond to changes in the electrical capacitance between the pickup elements and the reeds incident to vibration of the reeds.

2. In an electric piano the combination of a plurality of elongated substantially fiat reeds, reed support means supporting each of said reeds at one end thereof so that the reed cantilevers freely away from the support means therefor, each of said reeds having two longitudinal edges and defining on opposite sides of the reed two generally fiat longitudinal side surfaces, each reed being shaped to have a thickness perpendicularly to said reed side surfaces which is limited to only a small fraction of the width of the reed to constrict free vibration of the reed to a vibratory path generally perpendicular to said side surfaces of the reed, means for impulsively exciting each of said reeds for vibration, a capacitive pickup element defining a pickup surface extending along one longiudinal edge of each reed in electrically capacitive relation thereto and in a position disposed beyond the reed laterally in a direction generally parallel to said side surfaces of the reed, each of said pickup elements and the adjacent reed being positioned in relation to each other so that said pickup surface on the pickup element is substantially flush with a plane containing one longitudinal side surface of the reed when the reed is in its at rest position and the pickup surface and reed are disposed generally on opposite sides of said plane, and electric sound producing means connected to said pickup elements and said reeds to respond to changes in the electrical capacitance between the pickup elements and the reeds incident to vibration of the reeds.

3. In an electric piano the combination of a plurality of elongated substantially fiat reeds, reed support means supporting each of said reeds at one end thereof so that the reed cantilevers freely away from the support means therefor, each of said reeds having two longitudinal edges and defining on opposite sides of the reed two generally fiat longitudinal side surfaces, each reed being shaped to have a thickness perpendicularly to said reed side surfaces Which is limited to only a small fraction of the width of the reed to constriet free vibration of the reed to a vibratory path generally perpendicular to said side surfaces of the reed, means for impulsively exciting each of said reeds for vibration, a capacitive pickup element defining a pickup surface extending along one longitudinal edge of each reed in electrically capacitive relation thereto and in a position disposed laterally to one side of the vibratory path of the reed, each of said pickup elements and the adjacent reed being positioned in relation to each other :so that said pickup surface on the pickup element and the adjacent longitudinal edge of the adjacent reed mutually overlap in the direction of reed vibration when the reed is in its .at rest position but to a degree which is much less than the thickness of the reed, and electric sound producing means connected to said pickup elements and said reeds to respond to changes in the electrical capacitance between the pickup elements and the reeds incident to vibration of the reeds.

References (l'ited in the file of this patent UNITED STATES PATENTS 1,915,858 Miessner June 27, 1933 2,180,122 Severy Nov. 14, 1939 2,309,703 Levell Feb. 2, 1943 2,542,611 Zuck Feb. 20, 1-951 FOREIGN PATENTS 434.421 Great Britain Aug. 27, 1935

Claims

1. IN AN ELECTRIC PIANO THE COMBINATION OF A PLURALITY OF ELONGATED SUBSTANTIALLY FLAT REEDS, REED SUPPORT MEANS SUPPORTING EACH OF SAID REEDS AT ONE END THEREOF SO THAT THE REED CANTILEVERS FREELY AWAY FROM THE SUPPORT MEANS THEREFOR, EACH OF SAID REEDS HAVING TWO LONGITUDINAL EDGES AND DEFINING ON OPPOSITE SIDES OF THE REED TWO GENERALLY FLAT LONGITUDINAL SIDE SURFACES, EACH REED BEING SHAPED TO HAVE A THICKNESS PERPENDICULARLY TO SAID REED SIDE SURFACES WHICH IS LIMITED TO ONLY A SMALL FRACTION OF THE WIDTH OF THE REED TO CONSTRICT FREE VIBRATION OF THE REED TO A VIBRATORY PATH GENERALLY PERPENDICULAR TO SAID SIDE SURFACES OF THE REED, MEANS FOR IMPULSIVELY EXCITING EACH OF SAID REEDS FOR VIBRATION, A GENERALLY FLAT CAPACITIVE PICKUP ELEMENT DISPOSED ALONGSIDE ONE LONGITUDINAL EDGE OF EACH REED IN GENERALLY PARALLEL RELATION TO THE AT REST POSITION OF THE REED, EACH OF SAID PICKUP ELEMENTS HAVING A THICKNESS EXCEEDING THE THICKNESS OF THE ADJACENT REED AND DEFINING A PICKUP SURFACE EXTENDING ALONG THE ADJACENT LONGITUDINAL EDGE OF THE ADJACENT REED IN ELECTRICALLY CAPACITIVE RELATION THERETO AND IN A POSITION DISPOSED BEYOND THE REED LATERALLY IN A DIRECTION GENERALLY PARALLEL TO SAID SIDE SURFACES OF THE REED, EACH OF SAID PICKUP ELEMENTS AND THE ADJACENT REED BEING POSITIONED IN RELATION TO EACH OTHER SO THAT ONE EDGE OF SAID PICKUP SURFACE ON THE PICKUP ELEMENT IS SUBSTANTIALLY FLUSH WITH A PLANE CONTAINING ONE LONGITUDINAL SIDE SURFACE OF THE REED WHEN THE REED IS IN ITS AT REST POSITION AND THE PICKUP SURFACE AND REED ARE DISPOSED GENERALLY ON OPPOSITE SIDES OF SAID PLANE, AND ELECTRIC SOUND PRODUCING MEANS CONNECTED TO SAID PICKUP ELEMENTS AND SAID REEDS TO RESPOND TO CHANGES IN THE ELECTRICAL CAPACITANCE BETWEEN THE PICKUP ELEMENTS AND THE REEDS INCIDENT TO VIBRATION OF THE REEDS.