[1]Patented Mar. 23, 1954 21672,781 UNITED STATES PATENT OFFICE 2,672,781 VIBRATORY REED ELECTRONIC MUSICAL INSTRUMENT Benjamin F. Miessner, Harding Township, Morris County, N. J., assignor to Miessner Inventions Inc. Harding Township, Morris County, N. J., a c@r;oration of New Jersey AppHeation October 15, 1951, Serial No. 251,363 11 Claims. (Cl. 84-1.15) This invention relates to electronic musical instruments utilizing clamped-free vibratory reeds as tone generators and more Particularly to a novel arrangement of the translating devices associated with su6h reeds for the production of 5 desired tonal effects. The complexion of the output tones of a iensioned-string piano is markedly affected by the natural frequency and energy-damping charac@ teristies of the piano soundboard which effects 10 are known as formant action or as formant effects. These generally occur within a single cycle of vibration but may extend over a number of complete cycles before extinction by more or less string damping influences, in which case they 15 are more properly classed as broad-band resonant effects. Both kinds are present in piano soundboards but they will be referred to herein as formant effects because of their tone quality forming action. In essence, this formant action 20 involves the,generation of broad bands of vibration frequencies varying in mean or average value from one end of the piano bridge system to the other. Such vibration frequencies arise both by hamrner impact action on the tensioned strings 25 and by forced and resonant action and reaction between the strings and the bridge-soundboard structure. If, for example, a C keY for a 130.8 ey-cle per seednd, lower register string be struck and the bridge-soundboard structure in the region 30 of such string has a broad frequency response spanning 130.8 C. P. S., the bridge-soundboard structure will readily accept the 130.8 C. P. S. vibration partial I of the string. In fact, the integrallyrelated vibration partials of the string, and will radiate all such vibration frequencies as long as the string continues to vibrate. For those vibration frequencies of the soundboard having the strongest coupling, to.-e er with efficient radiation or other damping losses for strings having a group gf @ partials within the soundboard's strongly coupled band of frequencies, those string partials within this band will be relatively more rapidly damped than other partials of the String. Also, for these frequencies the bridge-soundboard structure will @eact back on the string to influt ' n vibration, in the manner of, all ence couple-d, re,@so-nant vibrators, mechanical or elee@ @ is t"i i ac 10 to make those vibration Partials which a,e rapidly transferred. to ihe soundboard of str(llg, iti in i al amplitude. and @horter tirae constant. structure will also accept the higher numbered, 35, An object of this invention is the provision of 2 ersbly, no direct sound radiation of the tone generators and the introduction of the formant effect into the audible tones of such instruments must be accomplished without a soundboard as such. An object of this invention is t]@e provision of means for producing conventional soundboard effects in an electronic musical instrument utilizing beam type vibrators as tone generators. An object of this invention is the provision of a novel mounting arrangement for translating means associated with vibratory reed tone generators. An object of this invention is the provision of novel and improved means for coupling vibratory reeds, in an electronic piano employing such reeds as tone generators, to provide improved output tones throughout a wide pitch range. An objeet of this invention is the provision of means for producing formant effects in an electronic piano empl(jying vibratory reeds as tone generators together with means for selectively varying stich effects to produce loutput tones of desired character. An object of this invention is the provision of a tone-producing Assembly for an eiectronic musical instrument said assembly comprising a series of tuned 61amped-free reeds secured to a reed rail, vibration-translating pick-ups I associated with the reeds, pick-up supporting means secuted to I the reed rail, a vibratile support for the p I ick-up supporting means, and electro-magnetic means for vibrating the vibratile support in a predetermined. manner. a tone-producing, assembly for an electronic musical instrument and comprising a series of vibratory reeds and associated pick-ups mechan40 @ ically co;upled to a common reed rail, a rigid base, resilient members disposed between the reed rail and the base, mechanico-electro-acoustic means for translating reed vibrations into sound, electromagnetic means for vibrating the reed rail, and 45 an electrical feedback circuit connected between theelectro-magnetic means and the electroacoustic means. These and other objects and advantages of the inventiorx will be apparent from the following cal @be liet acoustical effect of the formant r)O description when taken with the accompanying drawings. It will be understood the drawings are for,purposes of illustration and are not to be eonstrued as defining the scope'or limits of the lnvention iefer6iice being had for. the latter purpose in electronic znusical lnptr=ents there Is, pref - 55 @ to the appended claims.
[2]3 In the drawings wherein like reference characters denote like parts in the several views: Mgure 1 is a curve illustrating the relative amplitudes of the vibration partials of a tensioned string mounted on a massive, non-vibratile support; Figure .@.2 isi@w ourve,thvwingithe @variation- Of the amplttude of a soundboard'(of 0, high quality, large-size, grand piano) related to the vibrashown in Mgure 3; ]Figure 5 is a cross-sectional view taken along the line A-A of Figure 3; Flgure 6 is a side view of the assembly,sbown in Mgure 5 and including- .,a diagrammatic show- '20, ing of my arrangement,for vibrating the reedpir,k-up assembly, @ to @@ provide @ d6sited 'I, formant effects @Figure.@.7.49 similar to@FIgur-e@6, w-ith thelelec-'@, trical@ components omitted, and,@ showing, a@@7modi-' fication of the invention wherein the Plate sup-@ porting @the @pick-ups is inadel@of non-magnetic material,, Pigure 8: is a plan view, similg@t,to Fligure. @3, and showing another @ construction; of @'the@; pick-ups so 4 board for different frequencies along its length from bass to treble ends, etc. Since the soundboard is, in effect, an upwardly and convexly arched membrane of irregular shape and variably loaded by the bridge, and since s p e nW@6rdly by, the preeaure . ings sir equilibrium p@sltim, own upwardly acting ebmpliance, bration frequency varies along the entire bridge in and their@supporting postg; . @@ moisture and, its natural @ vibration@ @frequencies, @ Mgure@ 9'is a@ longitudinal-, cross-sectional vieiv.@ will@ @be@lowered'du e;to,the,;added lo,iiding-effect of @thls, water @ content - a,@nd@the; rise in its@ intemal vibrational'resista nce,@jwhereby, the output @tones w-ill @have a @- higher @damping,rate;an d will sound@ dull and lif6l6ss@ - Irk. tests :rrmde on i 9 small -grand @piano I' have found,@that,the@,natumi-Vibration frequencies@of the,--,soundboard varied @smoothly ifrom 90@,to 550, cycles .@per t secondz between @the two extreme ends @.@ofi@the:@bam and-@,treble@- bridges. In@@thellarger grand,. @ pianos @ the@ @frequency ange has, a r larger spread@andc the @lfrequency veriation is more uniform over@the@scal erange., ,Flgure 2,isa@-curv-e@showing.@the@vibration amplitude @of -,a @soundboardi atpositions limmediately,@belowstrings,@,havlng:the indicated undamental@,.frequencies of; alargert-size4 grand piano of Luropeo6n:.manufacture,,.@1 Superimposed -on such curve 4$ @a;@ similar curve;tof an@ ideal soundboard. soundboard,,thethickriessof4thetoundboard@and.@ - amplitude.@..Another,.string,having,afundamenthe @ nature,:of its reinfpreing, irib@,, . the @ sneiiie tal vtbrattorX_fr@pql4qncy.,of..45,0.,Q, P. S,. wguid have shtpo@ @of @@the soundooard,@,the,,UiterDia,-@.resistivol 'E@levAte,cl constantt,:of'@,tbL-@,.materi;tl.'of ii@g,: at @:the point C) while its partial n of 90 ar6 -made,,the radiati6n,;efficieAcy:,of,@@ ho.soUnd-@ Wglgd, p!oiut @"Chiet. , ft4ere,5t, . here is the fact that the soundbo ard frequenc y and damping charac @istimr markedl y,@affec t.@the complexi on of the outputto @ies by formant action, and this tonal compILi xion varies, or shifts,., along the pitch scale of every such instrume nt, in a way which is determin ed chiefl3t 7;by these formalit - effects. in addition,. ,to the; net,@- ,overall,- differenc e, in@, the formgnt, effect @as,eqt ablished by-the initial physical - relations h-ips of,, the coupled perts,, the damping rate-of the soundbo ardivarie s with humi dity@. For example, a Piano with a,soundb oard having littit, or @no; zmoistur e,@,cont ent will sound @ bright aridf erisg. I With@. continue d exposur e to hlgh humidity atmosph ere the@sou ndboard @will ebsorb' tion frequency of the immediately proxiinate@ 10@@ a,manner that is diffteult to calculate or, in fact, tensioned string, i,cIUV4cAte:@in-ivW-,,giyen number of instruments. Figure 3 is a fragmentary, top plan view of af, @Piam, a made by the same manu ae urer reed and pick-up assembly made in aceordance which appeor, outw Oly, quite identical in ea r with my invention; sigli@ atid- 'e.omtrdcttqn-- will sound differently in Flgure 4 is a front elevatton,@,of the -a3semblY--, 10 @.the. s respowe ifrequency;. close@ to that of :the adjacent strings @ and such curve should@ be sinooth@; starting at about@30 cycles@,,per,se cond and@@ending: at: 4,,000 to@@5,000 cycles per.- @second. Then the correct, tmpedanee@.-., Tnatching for, uniform@ energy transfer @ from @ the - irtrings to the, @ sounaboard would' obtain @And,..therei would @be no regions of the@ scaleywhere@. the tone quality would @be, markedly.- different@@ For examl3,1,e,@lif ar@bridgecoupled @.- string:- having:@a fundamental @pitch of @@500@'eyele s per .@ sec!Dnd. is, vibratad 11 adjacent @ to an actual soundboard having@@the iresponse characteristics shown,@in@IF Igure 2 the@ fundamental vibratiozi of the,,strirlg,@ falling at S,@lo,# @)pointA@ on.. the, ewte, would@e@dep ressed'in,,amplit ude. Howeverltho,vi bration@ partial 11 i.D@f @such string, bas. a:freq4ency of .1,000 C. P.,S. fallb@g at,the@relativel y high@point B,,on the curve and,.cQnsequen tly, thisvibration partial is elevated, @ relatively, .in, output sound softne4s and length %)f:theistriking hammer along150,@@IdeaUy; of @course; the Isoundboard'should have a 2,672,781 taken@ along @the line A ---- @A@ of Figure 8 " and Figure 10 is a cross-sectional view similar to that @of 'Figure, 9, @and showing -a@@ single pick-up 35 and@ supporting@ post@ of@ another construct@ion@-, dtawn to an enlarged scale, As@ ls;well. @known, the @initiall amplitudes of: the vibration partials of a tensioned string,@ mounted on a'. rigid base, are not@ equal :but,,@ rather, de- 40 crease @@ substantially,, @ ,unlformly @@ as the partial number inereases.@ @Flgure - ,I.illuotmtes.,the relative vibration amplitudes-.ofl:the first nine@vibra.:@ tion partials @of ja tensioned@ string,@tt being.i noted that the partials are integrally relatedand:@that the partials@higher-thanrpa rtial,,IV.@ha@ve an wnplitude.less than,orie@halt that of the.,fundemental partial,@I. - 'Ite .,,decrease., in.,@ amplitude from: one , to -the next @@higber, @ partial, is, 1 detervained chie,fly by @ the @ characteristics r @of i,the@,,string, the the string, .-and the specific@ ppint @on -the @rtrlng where the,harmner@strikes., However,,anyone,of,, these@ Partials may, be@ entirely,.absent, or of @ ab" normall@r lower'E@mplitude, @clue.,,to the @ damping. action,of..the exciter,bmmer during aetual iin- 50@@ pact with the string, :Tn, a@ pianp,.th6l striking, point,'along the @ptrin6,,; is so chosen that the Partiiii Vil@'is so,@elirninated, or ldelmped@ out. 'As -ttoted - @bovel-@ th(- bridgesoundboard'strueI Go tum-of -tL,ptano-hw a-broad@band -frequency cliaracteristic@ which@, varies, throug#out @ the scale of stiing.%-filom the,lower i@ndof,-the,bass@ bridge @to theupp6r end,;bf;theitteble,bridge. @-Many fac-' to'rs,influencethts-frequene characteristicfzloml y, point, to @'paint @@ along, ithe, scal6 - isuch - as;, the dis tribution of @the- thicknfts;- mass" and- lbngitudinal stiffness of the bridge, the bearing.,@-pressure@ of the,tensioned@strings, upon- the bridge, the @ proximity@,@of 'the bridge to@,@the ilxed edges @of.'the 70
[3]2,6,72i78l 5 D). Since the quality of a piano tone changes as the string vibration amplitude falls off, the first example tone, having its partial II damped out at a rate greater than partial I, will have a noticeably different quality than the second example tone subject to the reverse damping effect. Since soundboards are strongly damped mechanico-acoustic transducersi their vibrations do not continue much beyond the time confines of a few cycles of string vibration and their action is very closely similar to that of the formant effects in the mouth, nasal passages, larynx, etc. of the human voice apparatus. These members, in different individuals, produce different tone qualities at the same pitches due to the strongly damped but intra-eyelic resonant actions of these coupled resonators driven by the air puffs released by the vocal chords. In wind instruments, the formant action is varied from one instrument to another chiefly by the shape of the air column confined more or less within the boundaries of the instrument. In soundboard instruments employing the same kind of strings the formant action and output tone quality is varied from one to another chiefly by the soundboard design as to frequency and damping characteristics. In electronic musical instruments having no soundboard, such as instruments employing vibratory reeds for tone generators, the formant ef fects must be provided by an added e@lement whose vibration is induced by output of the tone generators and such induced vibrations is reintroduced into the translating system. In order to provide formant effects, in a vibraiory reed type of electronic musical instrument, simulating those of conventional instruments, the vibrational characteristics of the formant-producing sy@tem must correspond to those of the particular instrument being duplicated. Since the frequency dar-nping characteristics of soundboard instruments are not yet entirely known and since their damping characteristics are very difficult to measure by reason of their high absolute values, the duplication, in an electronic instrument, of a Particular conventional instrument must be accomplished by cut and try methods. When, however, the formantproducin,a system to be added to an electronic instrument is Provided with variable frequency and damping controls along the scale of the tone generators the e-ffects may be adjusted independently, until the listening ear accepts the electronically produced tode as comparable to the tone of a conventional instrument. In carrying out my invention, as applied to a clamped-free reed tYPe of electronic piano, I provide a vibratile support for the reed-v ibrationtranslating pick-ups which support is attached to the reed-motinting rail in such manner that the reeds, when vibrating, tend to vibrate the pick-up support whereby the translatiag system will translate the combined vib rations of,the reeds and of the pick-ups relative to onle another. Reference is now made to Figures 3, 4 and 5, Mgure 3 being a fragmentary top plan view of one novel mounting arrangement for the pickups, Figure 4 being a frorit elevation thereof, and Figure 5 being a cr6ss-s6etional vie* taken along the line A-A of ngure 3. The vibratory reeds I D@ I 1, 12, are clamped to the rail 13 by suitable, hardened set ser@ws 14,@ 15, 1 6, each sudh set: screl,v being alined with a co6perating similar screw siieh as the screw 15' shown in the crbsssectional view 6f Figiire'5, Thi@ reedi rail 13 is 6 ing unrestricted vibration of, the individual reeds. This particular reed-clamping arrangement offers numerous, practical advantages. Each reed is adapted for excitation, percussively or other@wise, by any suitable means and will vibrate in the direction indicated by the arrows a-a in Figures 4 and 5. The vibration-translating pickups, here shown as the capacitive type, comprise the individual metallic Plates 20 to 27, inclusive, 10 each plate being secured to the associated post 30 to 37 as by the screws 28, such posts being made of suitable insulating material such as a plastic. It may here be pointed out that the posts are internally threaded to accept the fastening i5 screws 28 and each of the pick-up plates is provided with an oversize hole whereby the spacing of the plate relative,to the adjacent side of the reed may set to a predetermined value before the fastening screw is tightened. Further, if the 20 plane of one or more of the pick-ups is to be altered with respect to the plane of the associated reed, when the latter is in the at rest position, this can be done by driving the insulator posts in one or the other direction in the holes provided in the 25 metallic plate 40@ The holes in the plate 40 are made slightly undersized relative to the outside diameter of the Posts whereby the posts will be self-supporting when driven into such holes. Alternatively, the plane of each individual pick-up 30 can be altered by placin.- shims between the pick-, up and the top of tbe supporting post. Each pair of pick-ups is so positioned that the transverse axis thereof coincides with nodal point for the vibration partial II of the intervening reed. Thus, @', 5 when the reed is excited by percussive means, such second vibration partial, which is dissonant relative to the reed's partial I, is eliminated from the translating system, The plate 40, preferably made of steel, is secured to the lower ,urface of 40 the reed rail 13, by screws located between the reed-clamping screivs, and is spaced from the plane 6f the reeds a distance sufficient to permit maximum amplitude of reed vibration. It will be.apparent the pick-ups are electrically insulated 4;-) from the reeds and that all reeds can be connected into -an electronic circuit by means of a single lead, attached to any part of the reed base 13 or plate 40, and that the pick-ups all can be connected by means of a lead secured to the ends of the fastening screws 28. Those skilled in this art will know the reeds and pick-ups form part of a radio-frequency circuit in which the oscillation frequency or amplitude is affected by the capacity between the reeds and the pick-Lips and such frequency or amplittide will be modulated by the change in capacity brought about Y)y vil)ration of one or more of the reeds@ relative to their associated pick-ups or of the pick-ups relative to the reeds. Such modulations are suitably amplified, demodulated, etc. to operate a loud speaker proOt) ducing audible tones. In order to superimpose desired formant effects into the audible output tones of the instrument I mount the assembly, shown in Figures 3-5, on a relatively thick, non-vibratile base and provide electro-rdagnetic, means.-,for vibrating the assembly in a specific iil-anner by feedback energy derived from the electrical output circuit of the pick-up system. 70 . Reference is now made to Figure 6 which shows the assembly of r4igure :51 comprising the reed rail 13, reeds I 1, pick-ups: 24 ahd the supporting plate 40, secured to. the. sid6 of a thick nonvibkat.ile base 45, by@ inean@- of screws 46, washibils provided with transverse holes 17, 18,@'@19 aff6id- 75 48. The ser6ws 46@pass through holes 46', see
[4]FigtM inereamit, fttlelf6r,ihepotntgBtt) E@, and'Pto G; t h e @ , 6 n e r g y ' . @ l m s e s ' @ m u g t ' @ b o - d @ e r e a s e d . ' % terial i'sucli@@as felt',;,rubbL-r,..,Vfn ylite,,etei,.may, be Iff-@a;@- tensioned@string@-@piano, each @stririg@'has@ cernalite&"to,@@both@@the,@-plate@'.40'@ and the .@base; 45. a :series@ of,"veryi@ribarlS@l"int6grally-relOted fteWhen,theireed@@ll@'isset'int6@@n,ormalvibration,as''5 quency, @iyarttau@whereat@a clamped '-free reed'has.@; indicate(r,,by -the arrows a, a@.,@- such,@vibro@tion will. no such fattutiate@'partial@fr6equeneyL relatibnship. tend,,,@ to 1, d6velop, t6rtloti-al @ vibrotion @'.of reed.. Th6!r@liti6nshloDf tuelf partial frequemies to the rail It 3:- as@!shown by tho- arrowg b@ b. @ This',@tends fundameuttLI @ftequeticy @'(Partiai I) @ ig as folloWS4 to-: dliveloij. an@ angular@ 'vibratiADn'.11(ofi@. vers,@@@SMUIl.:@ arnplitudie@;@relative,-t6'; thatlof,the struck reed). of'. lot, Freq F@'ofo,Parntial 0 the: plete"40.,t(Yward.and@@away frotn@the5@@reed M-. d nie tal@ shown,by@the@@arrow,s@c,,c' VibrtLtioh'of,the@reed@ base'.@i3@,,,an&,.df:@the.@plate@@40" Tengioned 'Clampedcornpliknee of "the,bend in theplate 40 tht,coin-@ String free Read t I ----- ------ ------------- I 1.01 pression@and,;.ComPItince,of he pgd@@47 as,well,'as@ 15@: by,,IU,@interna;l,viscositSr or@vibrgtiMall@resist4knc6., II ------------- ------ --------------------- 2 6.27 In,,a:@musical series,.of,tuiied@'@reL-dt@.tbe,lengtb@lof@ III ------ ----- -------- 3 17.-IS'@ IV__, ------------- ---------------------- -- 4 34.4 tbe,?iiidiVidual,@'reedi5@w,ill@"Vary; gerierally,',fr6ny a V ---------------------- ------------------- 5 56@,g mazinium@-in.@the 16,wr@frequeney'or@@bass@'sectidn' -------- ---------- -------- 6 85@O y' Lor tteblci% 20@@ to,&.@n)inimum,iin'the highi-fteciuene seetion.,@ Siri:te,.it@.is@:&Simble! ;to@position@@each' pair-,of "Piek'-Ups:,at ',the:nod9,1 point of 'Vibration paitiaIIIifor,.,;the,intervening.@reedj it'is:apparent@ the@vidth of@ the %pick,4up@silpportiligl,pig6tiE@ 40 will vaty,lh like,,manner,, ;I pref6t to make tht widtli@ 25@ ofl,the:.,Plater@@40,,a,bout'80,7o@.of@'th'e'le,igth of thcil in=ediately-e above-disposed reed sG @@ that' such plate, width@:wlll- -also%be.'A;-Irnaximum at,the! low frequeney reed'@@positioni.and a minimum@ at the the.plate-410 and@@the@,,elmtltity. of@the:material@of' which" the'Plat6'ii '@mode @ are so, chosen @ that@ the PlMe's@segmental@@@vibriati6ti,peri6diis about@equal @ un e immediateto -the f @ damentgl frequen)oi6s -of th ly:proximate@-reed6.' The,pl6,tLithiiDknet3s @lfor any 35 giveri:.@@pcdnt-"may;belfound@bY7fotming sucli@ a @t - , center t a - platelsegment@equal@ 0 the@eent6r to- p C', ing.L,.'of @the,,reeds' -, attachirig thereto a pair'of sup.@ port posts,, @pick@-ups and fbst6nirig screws to rep-.: reserit@th@e.@@aetu'al'@pla,te@- Iload,.cle,rnping such ar- 40 rangement, in @ w, viee, -vibrating the frt6@ end ' (@arrying the pick..@ups),@.arld@aetiiallY measuring the@, vibtation frequency@ The plate"40@ preferably@ is made of steel, for" PurPoses@ 'ta' b6,expliifted hereinbelow, and" its, leorreeti thickness@ is@ theLt'-whi6h 45 will give,@ a @ frequeries, 1 response - equal % to that of the@pridkiznate @reed" with dUe@'con8ideration belng given @to@,such,@;4factorgas,.the@ loadirig, provided by the@pick.@ups,.and,:their'sUpporting structilre. If neeessary@@ @holes rnay' be drilled @through the plate 50 to'raise the@ natural vibration, fr6quency @@tib(veits normal *alue or loading.rnemb46rs of'16ador,other material @may;@be added 'as - ,speeiflc'pointA,to 140wer@ the @natilral frequency,, all.,f6tttht purpo6eof @pro-@, ducing @.a; particular @and varying frequeticy, char@.@ 55 acteristiei'lalong,:the-.Plato,IL,nltthi@that'U the@@di@, mension,;in,@the@longititdinal@:@directi6n bf,@'the mil@' 13, @ Ihavelfound thst'-'fbr':reedA hmvthg ness@'of@- 0.032,;inch,,therplolte@@4o@I'm$tY:be@@made@'@of, Alinch@- thickL,steel@,in@order@tohavethe'approxi@.@60 mately correct frequency response'slorig,@the scale@ of -Teeds.@ Since,@the doinping chata;cteristies bf Ian actual, piano soundboard, @@s@@shovm: by:the- curve @of Fqk@. ure@21, a-Iso vary,.,along,@,.tht@.piano'brid'ge@,@.,this.@fi@c-' @65 tor vi bratloh@,simu.!;@.' latinr,pick@;u,p,supoort4'. O'.1 f trihls:.Purmsethe@@ width, @tbickness @ or: viset)stty@ 'of 'the@ pad, 47'maV,'., be varied, along the length of the plote,,-40@., E@y@ these, means the. desired Variation. of,, damping 70 may@ be obtained,@as @distin:,-uished from.an;other@ wise. smooth, curve,such!a&tli&.,curve of the ized'Isoundboard@@sbovm@ini.!Mgum,l; For,@.suctL@,:.@@ high,din@piixg:regWu&ai@,the@ poijita@@A;and,D@ When,. a@ tenstoiied@ string of a@ piano vibrati@s@ with @ v8Lrying pressure on; an associated soun'dbourdrv@ bridge@@ @ea;eh,.' and' all ' of ' its many@ and closely"spgeed @ vibration partittls produce, their own,.vvitiating, forcet @ on the; soundboard. , "ol other neighboritig@, and @ further, di@tant @'sti-iilgs hating@@one@or@more@,pEirtial frequencies equal to one@or,,Tnore@Partial8@'of':the excited; string; and: having-'More,or less@@coUpling'to!@it; will respond'@ high:ifrequeney.Nreed.@pGsitloh6 lbe,thickn6ss@of @ 30'by@'resonant vibrati6n producing a cornpli x@tone. Alsor; the hgLmnier@:impbct @on @the string is 2t@rans@. mitte d,,to, the%@st)undboard@'prodUcing- a 'wide @and continuous band of:'freVencies@iresultiiig@in tilt, chatacteristic , "thumpl,'@ or@ rap@"' In the, case of @ a.,l @cIsLmpe(l--fre6.:l reed'@ the @ vibration partlaii are,,-rnuch f urther@ separated; frequency @ Witer, and 1 y@ such @partia;ls are:@compl6tel lnhgrmoni Thus4l the nearest'reedi iib@ a Miltical scaIL& series of @tuned' reeds', havingi@ a:@near@ resonant @vibration, component., eqlual in @fretluency@ to partial I 'of an excited reed,will be@.rentovld by'a-frequency spiegdiof;' 6.27,@i times,,"@'the@ ftmdglniental@ frequency, of'the' struck reed'. , Sitch, frequency spread correspion& to'aboUt'21/2 octgves@ above, the:struck: re6d'or'a distgLn4*@equal t6 ahout 30@ reeds al6ng the reed' rail. Thli@@eoMps,'rL-S'with a spacing of'abbut'12' strings l in a converiti6i!al'piano. ConseqUelitl*' theleoupling, lh,a:@telitioned string piano Ls. tighter, than'.. iw, @'electr6nic; piano @ utilizihg ciainp'edfreell@, vlbriltory@ reed$.' Also, as alteady stbted, partitll@@ n of @ a; vibratory I reed'is @ di@sonant with partigl I. Therefotei the, partial vibrtttions of a reed *MI flnd@very?few, if any, resonant@partials, in a series of tuned r@eeds, to augment the@ translbted@'rLed" vit@rations. Bi@cause of@ these @@@and arrangem fa&,&% thL-@@atsemblY ent thus @ f @ar des cribed;: is4; ncit,l of -itsi@lf- suffibtent to provid6@ true,.toiiiii effd6ta@leorresponding'to those@of@@a given @.@eon'VtnttonAl musical'iiistrument' such as, for', 6xampl46" the plario. I overcome@ such defl'cie=Y@@b)r"iiitj76dii4birig int6 the'vibrgtile pick up suppbrt'. many @ @iiit@grally related ' vibrbtidn partials, sitch",partioli 'being produced- by the Pick-@ up, @fim the@ reed' vibration@ partigl I and'el6@@ @Vibratt tritally,'ftdtba;ck,,"to IZ on member assoct atect,"Iitach-support'.' The-@ fted.@bitek,., devi@e, coinpri@es, @ in, its t ele@6 mentsa @ forra, an,,a;djustalal@e, pcilirized core@ 501 surrounded by 6a coil 5 I.-: The coil, is secured in fixed @ position @within @ an appropriate @'Eiperture @-in b the @ ase, 45,,@ by,@ any suitable @means; and the- core 50.@may@ be,@threaded,to, operate-.Within@@.,the in.@, suiatoc, @u Pm, W-hich tboe6,coil,-is@,,,wound@.'.Sev@rdj i-al.@ such ea* arLd,@corw. sAsemblies@@- .a the ourve tlie.,da'nu-dng..or@euergy loma,,must@be;'@iW6@eDiced@i,,- ,at@..@intervals@@almg@@the-@,I"tu din al,@f,di.
[5]9 mension of the plate 40 and a I t different distances from the pick-up supports 34, as required. The coil or coils 50 are of low resistance and are connected across the voice coil of the loud speaker through an adjustable center tapped potentiometer 53. The reeds and pick-ups are connected to the translator circuit, as by the wires 55, 5-6 whereby the capacity variations between the pick-ups and vibrating reeds are converted into corresponding electrical waves which aredemodulated, amplified and fed to the speaker voice coil. As disclosed in my copending United States patent application Serial No. 169,714, ffled June 22, 1950, the pick-ups can be so.positioned relative to the coacting reeds that the wave form of the amplifier output current will Include a full series of Fourier series partials 1, 2, 3, 4, 5, 6, etc., times the fundamental vibration frequency of any one or more vibrating reeds. Such wave forms are fed to the coils 50 resulting in a vibration of the plate 40 (and the attached members comprising the reed rail, reeds, and pick-ups) in a manner corresponding to the normal frequency partials of the strings in a conventional piano. The phase of the feedback current may be made aiding or opposing, as referred to the partial I of the vibrating reeds, and of desired amplitude, by adjustment of the slider S on the potentiometer 53. Such adjustments Nvill depend upon whether more or less amplitude of partial I is desired in the output tones of the loud speaker. It will also be apparent the magnitude of the feedback current can be made still further controllable, as by a separate amplifier and controls fed from the speaker amplifier. When the reeds and pick-ups are so vi ra e , through the medium of the plate 40, a corresponding relative vibration occurs between the reeds and the pick-ups which vibrations are superimp6sed upon the translating apparatus tO correspondingly affect the audible output, tones from the speaker. With such an arrangement, then, the feedback currents contain all the component frequencies for setting up resonant vibrations not only in the octave-related reeds but also in those reeds having vibration partial frequencies of 1, 2, 3, 4 etc., or 1/2, 1/3, 1/4 etc., times the frequency of the excited reed. Furthermore, the broad, continuous band of frequencies of the vibratile pick-up-suPport plate provides innumerable other intervening frequencies corresponding to the "roar" of intermingled tones heard from a tensioned-string piano when played with the loud pedal depressed. Still further, the feedback-forced vibrations of the plate 40 will set up vibrations of the remaining, nonresonant reeds sirice such plate tends to vibrate, angularly, the fixed ends of all the reeds. It is evident from the foregoing disclosure that the formant effects characteristic of any type of soundboard instruinent may be siinulated. In electronic sustained-tone instruments, such as organs and the like, it is customary to use electrical formant circuits in an effort to simulate various conventional sustained-tone instruments of the direct acoustic type. Such circuits may also be used with my reed type mechanical vibrator instruments of damped or sustained tone type. it may here be observed that these prior electrical formant systems, having no direct coupling with the tone generating means and particularly no such coupling which varies note bY note through the pitch range according to the formant frequency characteristics of conventional instruments, can only be effective In the 2,672,781 @io particular pitch range for which they function. Such pitch range Is only of a length of two or three octaves in the musical scale. My direct mechanically-coupled electromechanical formant system can be so tuned and damped over its longitudinal dimension along the reed scale so as to secure any desired formant frequency effects in any or all parts of a scale having any desired pitch compass, or at least io to a practical extent within the limitations imposed by the human ear. While I prefer to make the vibratile plate, which supports the pick-ups, of magnetic material, the invention is not so limited. Reference 15 is now made to Figure 7 wherein the pick-up supporting plate 40, is made of nonmagnetic material such as, for example, aluminum. Vibration of the plate is brought about by a plurality of soft-iron rivets 59, one such rivet spaced from 20 each of the polarized cores 50. In the Mgures 3-7 embodiments of the invention the pick-ups comprise fiat, metallic plates secured to individual posts of insulating material. A preferred form of pick-up and mount25 ing axrangement, from the standpoint of facility of assembly and adjustment, is shown in Mgures 8 and 9. Here the individual pick-ups comprise a substantially U-shaped member 60 having offset ends 6 1, 62 lying in Planes parallel to that 30 of the reeds I 0, I 1, @ 2. The pick-up 60 is secured to an insulator bushing 63 by means of a screw 64 which passes through a clearance hole in the bushing into a threaded hole in the base of the Pick-up. The blishing 63 passes through a hole 35 in the plate 40 and is Secured thereto by a suita le nut 65. Thus, the pick-ups are insulated from the plate 40 and can be connected into the circuit by means of leads soldered to terminals disposed under the heads of the screws 64. It 40 will be noted that a single Pici-up is associated with two reeds and a slight amount of adjustmen etween the pick-up ends 61, 62 and the reeds can be accomplished by appropriately bending the body and ends of each Pick-up. The transverse center line Passing through the alined 45 ends of the pick-ups (such as the section line B-B of Figure 8) coincides with the nodal points for the vibration partial II of the reeds, for purPoses already explained. Mgure 10 shows another construction of the individual pick-up supporting Post for use with a U-shaped pick-up of the type shown in Figures 8 and 9. Here the pick-up 60 is secured to an insulator bushing 67 by the screw 64. The bushin- 67 is provided with an external thread which 55 cooperates with a threaded hole in the plate 40 whereby the plane of the pick-up ends 61, 62 can be adjusted relative to the reeds I 0, I 1. The bushing 67 is then locked in Position by the nuts 60 68, 69 which may be made of metal and of a type such as those used for mounting conventional toggle switches. Having now described several embodiments of my invention those skilled in this art will be 65 able to make certain desired variations and modifications in the individual components and their assemb ed relationship without thereby departing from the spirit and scope of the invention as set forth in the following claiins. 76 I
