US2545665A - Musical instrument - Google Patents

Description

March 20, 1951 M. J. LARsEN MUSICAL INSTRUMENT 2 Sheets-Sheet 1 Filed Aug. 5, 1949 Si@ n Tw w INVENTOR. AM/PW//VJ A/sfsf/v,

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A frR/VE y M. J. LARSEN MUSICAL INSTRUMENT March 20, 1951 2 Sheets-Sheet 2 Filed Aug. 5, 1949 Patented Mar. 20, 1951 MUSICAL INSTRUMENT Merwin J. Larsen, Villa Park, Ill., assignor, by

mesne assignments, to Central Comercial Industries, Inc., Chicago, Ill., a corporation o Delaware Application August 5, 1949, Serial N o. 108,706

19 Claims.

This invention relates to electrical musical instruments of the class employing sources producing complex audio signals at the tone frequencies of different notes of the chromatic scale, which signals are adapted to be selectively translated into audible sounds in response to actuation of the playing-keys of a keyboard. An instrument of this class is fully disclosed in Letters Patent of the United States, No. 2,403,090, granted to me on July 2, 1946.

In the aforementioned Letters Patent, the signal sources consist of high vacuum tubes, the complex output waves of which are conducted to wave filters by means of which they are repeated as waves of different harmonic composition and then impressed on the input circuit of an electroacoustical translating device and reproduced as audible sounds of different timbre.

An essential object of the invention is the provision of an organization of elements for producing pleasing sustained tones by an exceedingly simple and inexpensive system of transmission and keying-circuits.

The herein disclosed embodiment of my invention employs sixty sources respectively providing tone frequencies embracing a range of iive octaves, such that the lowest fundamental frequency is approximately 65. cycles per second. In organ nomenclature this range of sequential frequencies is known as a basic 8-foot stop. Most pipe organs embodt7 what are known as couplers. These are designed so that tones in given frequency relation are available in diferent combinations, i. e. the basic B-foot tone can be coupled to a tone which may either be a 4-foot tone an octave above said basic tone or a 16-foot tone an octave below said basic tone. With the organ, the player can selectively draw one or more coupler stops as may prove most useful for musical expression.

It is well known that when a tone of a given fundamental pitch is coupled to tones of other given pitch, the combination or resultant tone is more brilliant and has body the Single tone lacks. While a feature of the invention is a simple and inexpensive method of coupling octavely related tones, the invention is not limited in this respect, for the reason that by very similar methods of coupling given frequency sources with each other, tones can be produced that are comparable to various mixture stops of an organ. For example, the stop known as the manual quint 5%-foot which sounds a fifth above the normal pitch of an 8-foot stop, or the octave quint which sounds a twelfth above an 8-foot stop can be very readily obtained.

In an electrical musical instrument the addition of selectively actuable coupler and mixture stops entails an expense that is prohibitive in an inexpensive instrument, and it is therefore a further object of my invention to provide a simple system or method of permanently coupling to each other tones in any given pitch relation so that the resultant tones are more or less comparable to tones produced by more expensive instruments.

A still further object is the provision of a simple and inexpensive coupling system for electrical musical instruments whereby tonal balance or necessary tapering of the relative amplitudes of tones is assured from top to bottom of the gamut, regardless of the pitch relation of individual tones comprising any given combination of tones.

A still further object is the provision of a system adapted to be embodied as integral parts of circuits of the various cascades of electron discharge devices employed herein for producing complex waveforms at different tone frequencies and by means of which there will be no robbing amongst frequencies drawn simultaneously from any single electron discharge device.

The novel features of my invention are set forth with particularity in the herein appended claims. The invention, however, both as to the organization of elements employed and the method of operation, together with additional objects and advantages will be fully understood from the following description of a specific embodiment of the invention taken in connection with the accompanying drawings, in which:

The drawing is a schematic view of the invention, in which Figures l and la are continuations of a common electrical network when the figures are arranged to dispose Figure 1a, at the right of Figure 1.

In the production of musical tones from tone frequency sources or generators producing waveforms of audio signals which are rich in harmonics, it is customary to draw on one such source or generator only for each basic note and ,to employ, in addition thereto, switching means to draw upon sources or generators having octavely related (or other multiple) frequencies. For example, in pipe and electronic organs, 8-foot tones are keyed by means of straight-forward connections to sources or generators, the output frequencies of which correspond in number to the vibration frequencies of notes associated with the different playing-keys of a keyboard. li-foot tones are produced by selectively drawing frequencies from sources or generators one octave higher than the basic 8-foot tones. l-foot tones are asiatica 3 produced by other switching means which draw upon sources or generators having frequencies one octave lower than the basic 8-foot tone. Similar coupling switches can also, be arranged to draw upon sources or generators producing 2-foot tones (two Octaves higher) or 22/3-foot tones can be Y produced by connections to sources or generators having frequencies nearest the third harmonic of the basic S-foot tone, and so on. In carrying my invention into practice, resort can be had to any of these coupling methods, and for the broad purpose of my invention, the term coupling as used herein shall not be limited to the coupling of octavely related frequencies.

In order to produce a low-cost instrument with the maximum richness of tone, it is expedient in one embodiment of my invention to permanently connect, in a special manner, the 4-foot and the iii-foot tones with the basic S-foot tones, thereby eliminating otherwise expensive selective switching and involved or complicated wiring and cabling. 'Io couple both 16-foot and 4-foot tones to 8-ioot tones from top to bottom of a keyboard having a range of ve octaves would require a number of sources which would be greater than the number of playing-keys of a five octave keyboard. In the instant embodiment of my invention, use is made of only sixty sources or gen erators embracing a frequency range of iive octaves, and by tapering the amplitudes of the 16- foct outputs supplied to the next-to-lowest octave keys and similarly tapering the amplitudes of the 4-foot outputs supplied to the next-to-highest octave keys, and omitting the l6foot coupling in the bottom octave and the 4-foot coupling in the top octave, highly satisfactory results are obtained, such that to the average ear it is diicult to discern the difference between this system of coupling and the more expensive system in which for each key in said keyboard there are three distinctive tones at octave separation.

In the accompanying drawing, it is assumed that the keyboard of the instrument has sixty playing-keys and that each separate key operates a single electric switch. Fourteen of these switches are shown and respectively designated KCI, KCtl-KCZ and KC5. Each separate switch comprises a Xed contact element it connected to ground Il, a xed contact element l2 connected to a. common output conductor i3 and a movable contact element i4, the latter coactive with the key so that when the key is fully eleN vated, the switch is ofi and contact element I4 is engaged with element It so that the current flow is to ground. Said common conductor i3 is connected to ground by a resistor i3 of 4.7 K. When the key is depressed, the movable contact element I4 engages contact element l2 and the switch is on The output conductor i3 connects all of said switches with a iiltering system for producing a number of tone qualities. This system consists of lters I5, ll and I8, connected by branch paths i9, 20 and 2i to said common conductor I3. The output leads 22 `from said filters are each thereof provided with a control switch 23. These leads connect at 24 to the input lead 25 of an audio amplifier 26 in the output circuit of which is a loud speaker 2l. The input circuit of the amplifier is provided with any well known volume control device 28.

The term generator as used herein shall mean any well known electronic or electrical device or source adapted to produce an output wave which is rich in harmonics as distinguished from a single or sinusoidal wave. Systems of this class are shown in the patent to Larsen et al. No; 2,410,883 and are entirely dependable for the pur pose of my invention. Said system consists of a plurality of sets of high vacuum tubes in which the tubes of each set are connected in cascade and function as frequency dividers, i. e. assuming that the frequency of stage Cl of the C cascade is 1046. c/s, the frequencies of the successive, (controlled) stages of said C cascade will be 523., 262., 131., and 65. c/s, In this manner, the outputs of the respective stages of each and every cascade will be at octavely related frequencies. While the frequencies are not divided exactly by a factor of 2 for each stage, the division is sufciently accurate for all practical purposes.

In my Patent No. 2,403,099 twelve similar divider circuits are employed. Each separate circuit consists of a controlling stage oscillating at a given natural frequency which corresponds to the vibration frequency of the highest note of a given letterA in the chromatic scale. Thus, there is a circuit producing outputs corresponding to the tone frequencies of all C notes, a circuit producing outputs at the tone frequencies of all Ct notes, a circuit producing outputs corresponding to the tone frequencies of all D notes, and so on, to and inclusive of a circuit producing outputs at the tone frequencies of all B notes. As the range of the herein described instrument is limited to sixty notes, there will bevsixty individual oscillator stages or five stages per separate divider circuit of the twelve similar circuits. In the herein disclosed embodiment of my invention, the twelve divider circuits are arranged in three groups of four similar circuits, each, such that one group consists of circuits respectively producing outputs for all C, Ct, D and Dit notes, a second group of circuits respectively producing outputs for all E, F, Ft and G notes and a third group of circuits respectively producing outputs for all Gt, A, At and B notes. To avoid unduly complicating the herein disclosed electrical network I have disclosed but one circuit of each of said groups and have designated them C circuit, E circuit and G circuit.

Referring to the group comprising the C, Ct, D and Dt circuits, only the C circuit is shown. This comprises coupled stages Cl, C2, C3, C4 and C5.

Of the group comprising the E, RF1? and G cir cuits, the drawings disclose only the E circuit which comprises coupled stages E1, E2, E3, E4 and E5.

Of the third group which comprises circuits Gt, A, At and B, the drawings disclosed only the Gt circuit, the same comprising stages Gti, GiiQ, Gt, Gilll and Gt.

Referring more particularly to the circuit comprising stages Cl, C2, C3J C4 and C5, it is noted that said stages respectively have output terminals Ci', C2', C3', C4 and C5. Terminal CI has a resistance Rl in series; terminal C2 a resistance Rd in series; terminal C3', a resistance Rl in series; terminal C-t, a resistance Rill in series; terminal C5', a resistance R83 in series.

The output of stage C2 is connected to terminal Cl and C3' by resistors R3 and R5. The output of stage C3 is connected to terminals C2 and Cd by resistors R6 and R8. The output of stage C4 is connected to terminals C3 and C5' by resistors R9 and Rl l, and as shown, the output of stage C5 is connected to terminal Cd by resistor R i 2.

It follows from the above description that stages Cl and C5 are each thereof provided with a potential divider comprising two branch resistive output channels through which portions of a waveform of voltage is adapted to be concurrently conducted and that each stage C2, C3 and C4 has a potential divider comprising three branch resistive output channels. As each separate cascade of the twelve cascades herein employed is similarly designed, except as will be hereinafter pointed to, the resistances in the output channels of all similarly situated stages are designated by like reference characters and numerals.

Referring now to the manner of connecting the various stages in a keying and transmitting network, I have shown key-actuated switches of a keyboard employing sixty playing-keys. I have also shown a single key-actuated switch for the playing key for the last note in the top octave. It is noted that terminal CI' connects to the movable contact element I4 of switch KCI; that terminal C2 similarly connects with switch KC2 an octave above KCI that terminal El' connects with switch KEI and that terminal Gill connects with switch KGiiI. It accordingly follows that from terminal CI there will be impressed on switch KCI a wave which is the sum of the coupled outputs of stages CI and C2. Stage CI provides a frequency equal to 65. cycles per second (basic 8-foot tone) stage C2 producing a frequency equal to 131. cycles per second (an octave above CI). Similarly, the El terminal from stages EI and E2 impress on switch KEI a wave which is the sum of waves corresponding to 8foot and 4-foot tones. In like manner, terminal Giil conducts to switch KGtI a wave which is the sum of 8-foot and 4-foot tones. In like manner all remaining switches comprising the lowest octave will be similarly connected by their leads to their respective' stages.

Regarding the three intermediate octaves, each playing-key will be supplied with a wave which is the sum of -foot, 4-foot and 16foot tones. Only a connection to one switch, namely KC2 of the three intermediate octaves is shown, but on referring thereto it is noted that terminal C2 which connects therewith conducts thereto a wave which is the sum of the outputs of stages CI, C2 and 0C3, whereby the resultant tone will be a mixture of 4-foot, 8-foot and 16foot tones. All intermediate switches comprising the three middle octaves will be similarly connected.

In order that there will be no robbing amongst divided portions of the output of any generator that is simultaneously drawn upon, the resistances in the output of each separate stage are high relative to the internal impedance of said stage and the impedance of the load circuit.

An important feature of the invention is the herein disclosed use of twelve divider or equivalent circuits for producing frequencies through- 'out a useful musical range, which circuits are arranged in groups, such that each separate group comprises a given number of similar circuits. By this is meant that except that each separate circuit in any group furnishes its own or preassigned octavely related frequencies which correspond to the vibration frequencies of notes of the same letter of the chromatic scale, the resistances, coupling and tapering and anti-robbing of all circuits comprising any group are of the same values. By the method employed the high frequency tone signals are increased in amplitude by lowering, in groups, the values of resistors RI 2 for the 4-foot outputs and RIS for the 8-foot outputs, which increase is necessary to compen- 6 sate for the wave lters I6, I1 and I8 beyond the key switches.

The following table discloses the grouping of different sets of circuits and the various values of resistances in the outputs of the different stages:

Table of values and divider circuit grouping Group l Group 2 Group 3 Footage Terminal Resistors C, C#, D, E, F, FSI, G#, A, A#,

D# G B l R1 470 K 470 K... 470 K 2 R4 470 K 470 K.-. 470 Kv 8-Ioot- 3 R7 470 K. 470 K.. 470 K 4 R10 470 K 470 K. 470 K 5 R13 220 K 150 K 100 K 2 R2 3.3 Meg 2.2 Meg 1.5 Meg. 164cm 3 R5 820K. 0K... 820K 4 R8 820 K. 820 K. 820 K 5 Rll 820K 820 K U.- 820 K l R3 680 K 680 K 680K Moot 2 R6 680 K. 680 K 680 K 3 R9 680 K 680 K. 680 K 4 R12 330 K- 220 K 150 K hK is used to designate one thousand ohms-i. e. 470 K=470,000 o ms.

l1lII/eg. is used to designate one million ohms-i. e. 1.5 Meg.=l,500,000 o s.

While I have selected a practical grouping of the divider circuits, the total number of which consists of twelve such circuits arranged in groups of four circuits each, this is by way of illustration and in order that any person skilled in the art can satisfactorily practice the invention. I do not intend, however, to be limited in this respect as the number of individual tone frequencies comprising any group will depend upon the number of octaves comprising a given note or frequency range, to which can be added the total number of outputs desired to be connected to the keying circuits.

All of the aforementioned switches connect to the common output I3, so that when any selected switch is in an on condition, the Output of Vgenerators associated with said switch will be impressed on the wave lter system, thence impressed on the input circuit of the power amplifier 26 by selected actuation of the aforementioned switches 23. The wave filter system may be of any well known type so that the resultant tone will approximate a tone of any given timbre. The wave lter system shown and fully described in my Patent No. 2,403,090 is entirely suitable for the purpose of my invention.

The fundamental frequencies indicated upon the accompanying drawings are related to the standard frequency A=440 c/ s.

Particular Stress is placed upon these features of my invention which consist in providing a potential divider in the output of each separate electron discharge device as provided for by the impedances in said output.

As will be observed by referring to the table of values and divider circuit grouping, the 16- foot signals supplying the next to lowest octave switches are attenuated increasingly as the frequency lowers in three steps, each step comprising four notes. In addition to providing tonal balance this feature serves to blend the amplitudes of the signals so that no abrupt change is noticed at the junction where the 16foot signals are omitted, as between key KCI and key KC2.

At the other end of the keyboard, however, the 4-foot generator signals are not attenuated. In fact, they are increased slightly, in groups, within the next to the lowest octave. The reason for this is that the attenuation in the further networks more than compensates for the increasing generator signals.

Tone frequency sources as used herei-n shall be construed to mean any well known electron discharge device or generator for producing an output wave of predetermined audio frequency which is preferably but not necessarily a wave rich in its harmonic composition. a

While I 'have disclosed herein a system of frequency generators consisting of separate frequency halving circuits, any of the well yknown frequency multiplying circuits may be used to full advantage.

I claim:

1. A musical instrument of the class employing a keyboard, each playing-key of which is provided with a single electric switch which is actuable from an off condition when the key is elevated to an on condition when the key is lowered; said instrument comprising a plurality of divider circuits, each comprising oscillator stages connected in cascade and including a controlling first stage operating at a given natural frequency and a plurality of controlled stages, said controlling stage and said controlled stages respectively producing output Waves at octave separation and each having an output terminal permanently connected to an assigned one of said switches; and impedances in each separate divider circuit, Isaid impedances connecting preassigned stages with preassigned output terminals, whereby the wave impressed on any single terminal and on any single electric switch is the sum of output Waves of at least two of said stages.

2. A musical instrument of the class employing a work circuit, and a keyboard, each playing-key of which is provided with a single electric switch which is actuable from an Off condition when the key is elevated to an on condi-tion when the key is lowered; said instrument comprising a plurality of sources respectively producing output waves at tone frequencies for more than two cctaves of notes of a musical scale, each of said source having an output terminal permanently connected to a preassigned one of said switches and v provided with an impedance of given value, said source also having an output path in addition to the path provided by said terminal, the same connected to theoutput terminal of another one of said sources, whereby in addition to conduction of the output from any source to a pre assigned switch there is conducted to the same switch the output wave from ancther source.

3. A musical instrument as set forth in claim'2, wherein the additional output path yfrom each separate source has an impedance, the value of which is different from that of theirnpedance of the output terminal of the same source.

4. A musical instrument as set forth in claim 2, wherein the additional output path from each Aseparate source has an impedance, the value of which is different from that of the impedance of the output terminal of the same source and wherein both said impedances are high `relative to the impedance of said source.

5. An electrical musical instrument of the class employing a work circuit and a keyboard, each separate playing key of which is provided with a single electric switch which is actuable thereby from an o condition when the key is elevated to an on condition when the key is lowered; said instrument comprising a plurality of sources respectively producing complex output waves at tone frequencies for more than two octaves of notes of a musical scale, each vof said sources having 1an output terminal permanently connected to a preassigned one of said switches and `provided with 'animpedance of predetermined value, said source'also having an output path in addition to the path provided by said terminal and having an impedance of predetermined value, said additional path connected to the output terminal of another one of said sources, whereby in addition to conduction of the output from anysource vto a preassigned switch there is conducted to the same switch the output wave from another source, said switches connected with said load circuit and said impedances in the paths of any source, each being high relative to the impedance -of said source and the impedance of said load circuit.

6. `An electrical musical instrument as set forth in claim 5, wherein said work circuit includes means `for repeating the output of Waves fimpressed thereon as waves differing therefrom in their harmonic composition.

'7. An electrical musical instrument as set forth in claim 5, wherein said work circuit includes means for repeating output waves `impressed thereon as waves differing therefrom in their harmonic composition and wherein said work circuit has means for translating said repeated waves into audible sounds and of desired volume.

8. rA musical instrument of the class employing a keyboard, each playing-key of which vis `provided with a single electric switch, actuable b'y the key from an oi condition ofthe switch when the key is elevated to an onf condition thereof when the key is lowered; said instrument comprising a plurality of sources of complex audio signals having the vibrationffrequencies of different notes of a musical scale, impedances connecting eachseparate switch to preassigned ones of said sources, and means including'a conductor connected in common lto all of said switches for transmission of signals to an electroacoustical translating system.

9. A musical instrument as setforth in claim', wherein said sources comprisehigh vacuum tubes providing separate sets of tubes in which 'the tubes of each set are connected in cascade and aration.

10. In va musical instrument employing wave filters and sources respectively vproducing compleX waveforms of audio signalshaving the tone frequencies of different notes of a musical scale, a playing-key actuated switch -for and connected to each separate one of the aforementioned sources, impedances coupling preassigned sources withpreassigned switches such that signal Voltages conducted to any individual switch is the sum of signal voltages from'respective sources, a common conductor connected 'to 'all of said vswit'chesand. tosaid filters, and'means enabling selective conduction of the outputs of saidiilt'ers to the input circuit of anelectroacoustical translating system.

l1. A musical instrument as set forth inclailn 10, wherein the values of said impedances are such thatithe'relative amplitudes of lsignal vvvoltages conductedto `a switch` from coupied sources are relatively different.

l2. vIn a musical instrument employing sources respectively producing audio-signals `at the tone frequencies of sequentially related tone signals for arrange of more than two octaves; said in strument comprising in Vconflbination `with each separate one of said sources a single electric switch adapted to be actuated by a playing-key of a keyboard, impedances of predetermined values coupling the outputs of preassigned sources to preassigned switches such that there is selectively impressed on any single switch at least two signals of different frequency, said impedances serving to x the amplitude relation between signals of different frequency impressed on any switch.

13. In a musical instrument of the class em-V ploying a keyboard, each playing-key of which is provided with a single electric switch actuable from an off condition when the key is elevated to an on condition when the key is lowered, said instrument comprising a plurality of sources of audio signals having the vibration frequencies of musical notes for a range of more than two octaves, each of said sources having a potential `divider providing a plurality of parallel paths,

each having an impedance of predetermined value, a switch for and individual to each of the sources, said paths connecting individual switches ,with a plurality of preassigned sources such that ythere is impressed on each individual switch a waveform of voltage which is the sum of signal voltages from said plurality of sources, the values of said impedances in said voltage dividers being predetermined so that the amplitude of one frequency component impressed on a switch is greater than that of another frequency component impressed on the same switch.

14. A musical instrument as set forth in claim 13, wherein a load circuit is included and a common conductor connects all of said switches to said circuit, the impedance of said load circuit 4being low relative to the impedances in said parallel paths.

15. A musical instrument as set forth in claim l 13, wherein said sources are connected in sets in which the sources of each separate set are coupled in cascade.

16. A musical instrument of the class employing a keyboard, each playing-key of which is provided with a single electric switch which is actuable thereby from an off condition when Vthe key is raised to an on condition when the key is lowered; said instrument comprising as many tone frequency sources as there are playing-keys in said keyboard, each of which produces an audio signal corresponding to the vibration frequency of the note associated with a preassigned playing-key, an electrical network in which said switches and said sources are connected, said network including output terminals permanently connecting given lcries of said vsources to switches of preassigned playing-keys of said keyboard, paths connecting preassigned assigned ones of said devices with preassigned ones of said terminals are in groups in which the impedances comprising a particular group are the same but different from the impedances of another group.

18. A musical instrument of the class employing a keyboard, each playing-key of which is provided with a single electric switch which 1s actuable from an olf condition when the key is elevated to an on condition when the key is lowered; said instrument comprising a plurality of electron-discharge devices respectively providing sources producing output waves at tone frequencies for more than two octaves of notes of a musical scale, each of said electron-discharge devices having an output terminal connected to a preassigned one of said switches, and impedances interconnecting preassigned ones of said devices with preassigned ones of said output terminals, whereby the output wave at said preassigned terminals is the sum of output waves from a predetermined number of said electron-discharge devices, the impedances interconnecting the preassigned terminals of some of said electron-discharge devices being the same but different from the impedances of others of said devices.

19. A musical instrument of the class employing a keyboard, each playing-key of which is provided with an electric switch which is operable from an olf condition when the key is elevated to an on condition when the key is depressed, an audio amplifier having a loud speaker connected in its output circuit; said instrument comprising, twelve sets of tone frequency oscillators, the oscillators of each separate set connected in cascade to produce octavely related tone frequencies, said sets of cascaded oscillators arranged in separate note groups, the oscillators o1' each set of cascaded oscillators having an output terminal connected in circuit with a preassigned one of said electric switches; resistive means for each set of cascaded oscillators, said resistive means comprising resistances interconnecting the output terminals of the oscillators to each of said sets, the resistances in any given group of said cascades being the same but different from the resistances of any other group of cascades, a filter system having an output conductor connected to the input circuit of said audio amplifier, and a common conductor connecting all of the aforementioned electric switches to the input side of said filter system.

MERWIN J. LARSEN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,203,432 George June 4, 1940 2,227,100 Manatt Dec. 13, 1940 2,233,948 Kock Mar. 4, 1941 2,403,090 Larsen July 2, 1946

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