US3511918A - Electronic organ system utilizing band elimination filters for minimizing beat effects - Google Patents

Description

v Illa I l1 l l l I n l l I I n I l 1|J. 8 AI W E 5. mv... O` @L NmH0u\ojmo N AW we.. ....a.. m m QJ? L 7J m own Q J. r N d m 1 w T m Nmm om. mm v Q@ Do 7J EE mm wt om@ Em R y D w Emm w@ E: om@ EN memo. mmm o Ezmz .T.,,.......--4 m- B l n [IO n m k o QQN. QN M d DM mu. uw wu @m @n m m m.. ma 3 1- 1j 1- m m @www2 @www w n- @KSL HMT ..-m G onwmmm ooNN n m m 55mm ow u 0m om@ @DLV 7 T u.. m C r 1l1||||||a||| .wm www@ o EN MMU@ mm www@ n @N29 www Szm Q P. d. J U M United States Patent 3,511,918 ELECTRONIC ORGAN SYSTEM UTILIZING BAND ELIMINATION FILTERS FOR MINIMIZIN G BEAT EFFECTS Donald J. Leslie, Altadena, Calif. Leslie Research C0., 267 S. Fair Oaks Ave., Pasadena Calif. 91101) Filed Jan. 10, 1966, Ser. No. 532,485 Int. Cl. Gh 1/00, 1/06 ABSTRACT OF THE DISCLOSURE In order to avoid a major source of beat effects in an electric organ or other musical instrument having complex generators, the third harmonic is suppressed. Accordingly, the third harmonic of any note cannot beat with the second harmonic of the note in fifth musical interval relationship since the third harmonic doesnt exist. Also, the fourth harmonic of any note cannot beat with the third harmonic of a note in fourth musical interval relationship because the third harmonic doesnt exist.

BRIEF SUMMARY OF THE INVENTION This invention relates to electronic organs or similar musical instruments that generate complex signals corresponding to the fundamental and harmonic components of musical notes.

It has been well established that certain beat effects are present in such musical instruments. Thus, as explained in my prior patent No. 2,596,258, issued May 13, 1952, and entitled Electric Organ Speaker System, whenever two generators corresponding to notes in fourth musical interval relationship with respect to each other are simultaneously operated, the fourth and third harmonics of the respective generators are separated in frequency by only one or two cycles per second; and whenever two generators corresponding to notes in fifth musical interval relationship with respect to each other are simultaneously operated, the third and second harmonics of the respective generators are similarly separated in frequency by only one or two cycles per second. If a single electrical channel combines signals from such generators, then a new frequency component will be heard that goes on and olf at the rate of about once every second or two, and an annoying -beat effect results. Since fourth and fifth musical interval chords are common, such beat effects often occur. The beat effect is magnified by addition of tremolo and vibrato, such as by rotary apparatus shown and described in my prior patent No. Re. 23,323, issued Ian. 9, 1951, and entitled Rotatable Tremulant Sound Producer.

In certain organ systems, a set of generators spanning several octaves is derived from a set of twelve master oscillators. In such systems, the second, fourth and eighth harmonics of any generator are precisely tuned to the generators for octaves above and below since generators in octave relationship all derive from a common oscillator. However, the sixth harmonic of a generator has a frequency component that may beat with octave harmonics of a generator in fifth musical interval relationship.

In order to avoid such annoying beat effects, I have heretofore proposed various systems. For example, in said Pat. No. 2,596,258, two electrical-acoustic channels are provided for generators in alternate half-tone relationship whereby electrical mixing of signals of generators in fourth or iifth musical interval relationship is precluded. In my prior patents No. 3,041,910, issued July 3, 1962, entitled Electrical Circuit Arrangement for Complex Wave Generators, No. 3,049,040, issued Aug. 14, 1962, entitled Apparatus for Minimizing Beat Effects, and No.

3,080,786, issued Mar. 12, 1963, entitled Speaker System for Adding Tremolo, multichannel systems are illustrated for solving this problem. While these systems are quite satisfactory, the addition of an extra electrical-acoustic output channel s costly. Accordingly, the primary object of this invention is to provide a system for minimizing lbeat effects that requires but a single electric-acoustic channel.

The third harmonic component appears to be the major source of diiiiculty since it may beat with the second harmonic of another generator as well as the fourth harmonic of still another generator. Accordingly, if the third harmonics of all generators can be suppressed, the beat problem will be avoided even though the second and fourth harmonics of the generators remain. I have discovered that the third harmonic can be eliminated Without significant `loss of characteristic voicing of an organ. Thus only clarinet-type tone requires a strong third. Other tones are not seriously affected by the absence of the third harmonic. Accordingly, an excellent compromise is reached simply by suppressing the third harmonic. The sixth harmonic is never dominant in any tone; hence, its suppression goes without significant notice.

Another object of this invention is to provide a set of complex generators each having a harmonic structure characterized by the absence of the third and sixth harmonics.

This invention possesses many other advantages, and has other objects which may be made more clearly apparent from a consideration of several embodiments of the invention. For this purpose, there are shown a few forms in the drawings accompanying and forming part of the present specification. These forms will now be described in detail, illustrating the general principles of the invention; but it is to be understood that this detailed description is not to be taken in a limiting sense, since the scope of the invention is best defined by the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a chart illustrating the frequencies of harmonic components of generators for notes in fifth musical interval relationship;

FIG. 2 is a chart illustrating the frequencies of harmonic components of generators for notes in fourth musical interval relationship; and

FIG. 3 is a schematic diagram of an organ system incorporating the present invention.

DETAILED DESCRIPTION As shown in FIG. 1, the third harmonic of A (440) has a frequency that falls quite close to the frequency of the second harmonic of E (659.26). If generators corresponding to A (440) and E (659.26) are simultaneously operated and mixed in the same electricalacoustic channel, the listener will perceive a frequency component of about 1320 c.p.s. but which goes on and off or at least increases and decreases in amplitude at the rate of about one and a half cycles per second. Thus the frequency components 1320 c.p.s. and 1318.52 c.p.s. move into and out of reinforcing and bucking relationship at a rate corresponding to the frequency difference.

In FIG. 2, the fourth harmonic of A (440) has a frequency that falls quite close to the third harmonic of D (587.33). Accordingly, when generators for these notes are `simultaneously operated and translated in the same electrical-acoustic channel, the listener will perceive a frequency component of about 1760 c.p.s., the amplitude of which increases and decreases at a rate of about two cycles per second, corresponding to the difference in frequency between 1760 c.p.s. and 1761.99 c.p.s.

The charts shown in FIGS. l and 2 are typical, and it can similarly be shown that the third harmonic of a generator for any note produces like beat problems with the second and fourth harmonics of other generators. Accordingly, by suppressing the third harmonic for all of the generators, the source of such beat effects will be eliminated.

In FIG. 3, there is illustrated a set of generators 8.

Each generator of this set produces signals rich in all harmonics. A transducer for converting 'the electrical impulses into another form in the present instance is a speaker system 10. The speaker system is shown in this instance as driven by several electrical output channels 12, 14, 16, etc. Each of these electrical channels 12, 14 and 16 is controlled by a stop switch 18, 20 and 22 labeled, for example, Tibia, Oboe, Cello, etc. The number of electrical output channels is irnmaterial, but several are shown for illustrative purposes.

An electrical signal having a pitch C1 and a timbre corresponding to tibia is applied to the Tibia channel 12 by operation of a key 24. Associated with the key 24 are a series of key switches 26, 28, 30, etc. for the electrical output channels 12, 114, 16, etc. Thus when the key switch 26 is closed, a circuit is established from the generator C1 as follows: a lead 32, a band elimination lter 34 of conventional design, an isolation resistor 36, key

f switch 26, a lead 38, a shaping circuit 40 designed to impart suitable tibia characteristic to the signal, the stop vswitch 18, and the electrical output channel 12.

Similarly, the switch 24, when closed, transmits to the Oboe channel 14 a signal corresponding to the generator C1 but shaped to produce a characteristic Oboe tone. Thus a circuit from the generator C, may be traced through the lead 32, the band elimination filter 34, an isolation resistor 42, the key switch 28, a lead 44, a shaping circuit 46, and the stop switch 20 to the electrical output channel 14.

The key switch 30 operates in a similar manner in connection with the Cello output channel 16. Of course, a single key switch could serve in place of the switches 2'6, 28 and 30` which transmit a common pitch. Other switches of the set could be used for coupling purposes.

Similar circuits are provided for the other generators of t-he set `8. Thus, associated with the electrical output lead 48 of the generator D#1 is a band elimination filter 50 that connects to one side of key switches 52, 54 and 56 operated by a key 58. Serially associated with the switches 52, 54 and 56 are Tibia, Oboe and Cello shaping circuits 60, 62 and 164 that are interposed in leads `66, |68 and 70 to the electrical output channels 12, 14 and 16. In a well-understood manner the keying system for the organ is thus provided, only a few of the connections being shown by way of illustration.

Each generator, however, is provided with a band elimination filter, such as filter 34 or 50, that substantially attentuates the third harmonic. Thus the band elimination filter 34 for the generator C1 is tuned to the frequency corresponding to the third harmonic of C1, and the band elimination filter 50 for the generator `Dil is tuned to a frequency corresponding to the third harmonic of D1. The third harmonics of all of the gnerators accordingly are suppressed, and no beat effects occur due to the interaction of the third harmonics either with the lsecond or fourth harmonics of other notes. Of course, the second and fourth harmonic components of the generators are passed by the band elimination filters, the tuning of the filter being sufficiently sharp for this purpose.

Individual generators of the set 8 together with their filters 34 may as a unit be considered a generator circuit that produces complex signals containing the second, fourth and other harmonics of the note, but substantially devoid of the third harmonic.

If desired, the suppression devices 34, 50, etc. could be split into components and associated serially with the outputs of the shaping circuits 40, 46, etc. Optionally the shaping circuits could be located between the key switches and the generators.

Illustrated in dotted lines in FIG. 3 are band elimination filters 72, 74, 76, 78, etc., which are designed to suppress the sixth harmonic components. Accordingly, these harmonic components cannot interfere with the other harmonic components of companion generators of the set.

The inventor claims:

1. In an electrical instrument: a set of generators for producing complex signals rich in harmonics corresponding to notes in a musical range; an electrical-acoustic output channel; key switches for operatively connecting the generators to the output channel; and a set of suppression circuits for the generators, each suppression circuit being interposed 'between the respective generators and the electric-acoustic channel, each of said suppression circuits being individually tuned to suppress the third harmonic of the corresponding generator whereby beat effects with second and fourth harmonics of other generators are minimized; said -tuned suppression circuits imposing a characteristic to the instrument that compromises its versatility.

2. The musical instrument as set forth in claim 1 together with a second set of suppression circuits for the generators, each of said suppression circuits of the second ser being individually tuned to suppress the sixth harmonic of the corresponding generator whereby beat effects with octave harmonics of other generators are minimized.

3. In an electrical musical instrument: a plurality of selectively operable electrical output channels; common transducer means having an input connected to all of Said channels; a set of generators for producing complex signals rich in harmonics corresponding to notes in a musical range; key switch means for each of the generators; a set of circuits for the generators, each circui-t |being serially associated with the generators and said electrical outlput channels, and controlled by the respective key switch means, each of said circuits including shaping means for imparting characteristic -tonal quality, and each of said circuits also including individually tuned means for suppressing the third harmonic of the corresponding generator; said tuned means imposing a characteristic to the instrument that compromises its versatility.

4. The musical instrument as Set fotrh in claim 3 in which a common suppressing means is provided for all of said circuits for each generator.

S. The musical instrument as set forth in claim 3 in which each of said circuits also includes individually tuned means for suppressing the sixth harmonic of the corresponding generator.

6. In a musical instrument: an electric-acoustic output channel; a set of parallel input circuits for said channel, and corresponding to notes in a musical range; generator circuit means applying to said input circuits respectively, complex signals corresponding to the individual notes, and containing the second, fourth and other harmonics of the note, but substantially devoid of the third harmonic; means for individually keying said generator circuit means; and a plurality of selectively operable shaping circuit means separate from said generator circuit means and serially associated therewith for determining characteristic voices of the instrument.

7. In a musical instrument: an electric-acoustic output channel; a set of parallel input circuits for said channel, and corresponding to notes in a musical range; generator circuit means applying to said input circuits respectively complex signals corresponding to the individual notes and containing the second, fourth and other harmonics of the note but substantially devoid of the third and sixth harmonic; means for individually keying said generator circuit means; and a plurality of selectively operable shaping circuit means separate from said generator circuit means and serially associated therewith for determining characteristic voices of the instrument.

8. In an electrical musical instrument: a set of generators for producing complex signals rich in harmonics corresponding to` notes in a musical range; an electricalacoustic output channel; key switches for operatively connecting the generators to the output channel; and a set of suppression circuits for the genera-tors, each suppression circuit being interposed between the respective generators and the electric-acoustic channel, each of said suppression circuits being individually fixed and narrowly tuned to suppress the third harmonic of the corresponding generator while passing the second, fourth and other harmonics whereby beat effects with second and fourth harmonics of other generators are minimized.

9. The musical instrument as set forth in claim 8` t0- gether with a second set of suppression circuits for the generators, each of said suppression circuits of the second set being individually xed by and narrowly tuned to suppress the sixth harmonic of the corresponding generator while passing the ifth, seventh and other harmonics whereby beat etects with octave harmonics of other generators are minimized.

References Cited UNITED STATES PATENTS HERMAN KARL SAALBACH, Primary Examiner F. P. BUTLER, Assistant Examiner U.S. Cl. X.R. S11- 1.12

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