US3629482A - Electronic musical instrument with a pseudorandom pulse sequence generator - Google Patents

Abstract

Apparatus for producing complex rhythm patterns (rhythm ''''breaks'''') involving operation of a plurality of percussion devices in a pseudorandom manner. A clock pulse generator drives a pseudorandom pulse sequence generator having a large number of outputs on which appear a large number of different combinations of output pulses. Each clock pulse effects a change in the combination of pulses appearing at the outputs. The outputs of the pseudorandom pulse sequence generator are combined in logic gates having outputs connected to a plurality of percussion devices which are operated in pseudorandom manner (depending on the output pulse combination) at a tempo determined by the source of clock pulses. The source of clock pulses may be a free-running clock pulse generator operating at any desired one of various rates or may be derived from a musical instrument, e.g. an organ, so that the clock pulse rate (rhythm) is set by the player of the instrument.

Description

United States Patent [72] Inventors James K. Miller;

Theodore II. Shepertycki, both 01 Ottawa, Ontario, Canada [21] Appl. No. 831,641 [22] Filed June 9, 1969 [45] Patented Dec. 21, 1971 [73] Assignee Canadian Patents and Development Limited Ottawa, Ontario, Canada [54] ELECTRONIC MUSICAL INSTRUMENT WITH A PSEUDORANDOM PULSE SEQUENCE GENERATOR 3 Claims, 7 Drawing Figs.

[52] 11.8. C1 84/1.03, 84/ 1 .26 [51] lnt.Cl Gl0h 1/02 [50] Field of Search 84/1.01, 1.03, 1.26, DIG. 12

[56] References Cited UNITED STATES PATENTS 13226921 2/1969 Park 84/1.03 3,358,068 12/1967 Campbell 84/1.01 3,482,027 12/1969 Okamoto et al. 134/1 .03

Primary Examiner-D. F. Duggan Assistant Examiner-Stanley .l Witkowski Attorney-Smart and Biggar ABSTRACT: Apparatus for producing complex rhythm patterns (rhythm breaks") involving operation of a plurality of percussion devices in a pseudorandom manner. A clock pulse generator drives a pseudorandom pulse sequence generator having a large number of outputs on which appear a large number of different combinations of output pulses. Each clock pulse effects a change in the combination of pulses appearing at the outputs. The outputs of the pseudorundom pulse sequence generator are combined in logic gates having outputs connected to a plurality of percussion devices which are operated in pseudorandom manner (depending on the output pulse combination) at a tempo determined by the source of clock pulses. The source of clock pulses may be a freerunning clock pulse generator operating at any desired one of various rates or may be derived from a musical instrument, e.g. an organ, so that the clock pulse rate (rhythm) is set by the player of the instrument.

EXCLUSIVE on CIRCUIL 4o J on: or 10 UNIT osuws (FLlP-FLOPS) CLOCK if 0 2 L 3 4 5 s 1 e s H reusnces 0-9 0 o 2 3 4 5 s 1 a 9 lo HOUTPUTS/ m O-IO )Q I 1 OUTPUT 2s OUTPUT 2| OUTPUT 17 ONE POSSIBLE FORM OF PSEUDO-RANDOM SEQUENCE GENERATOR SHOWING 14 OF 1023 POSSIBLE OUTPUTS TO DRIVE PERCUSSION PATENTEU 05221 197i 3.629.482

SHEET 1 OF 3 Y PERFORMER ,0 ,3

SOUND r OUTPUT MUSICAL //5 J6 INSTRUMENT RHYTHM SOUND BOX PERCUSSION (PSEUDO OUTPUT RANDOM) /4 l6 P SEUDO- BOX SION UTPUT D MUSICAL SOUND PERFORME INSTRUMENT OUT 2 l4 PSEUDO- 5... SOURCE RANDOM To OF PULSE 1* CLOCK SEQUENCE 5$P g PULSES GENERATOR 20 2/ 23 PULSE PULSE SOURCE COMPARISON ON CIRCUITRY MUS'CAL INSTRUMENT F/GJ INVENTORS JAMES K. PULFER THEODORE H.SHEPERTYCKI AT ORNEYS PATENTED UECZI I971 SHEET 3 BF 3 PERCUS N IHIIIH DEVIC 2a g L D GIQ PERCUSSION RHYTHM W0 DEVICE [NOE PERCUSSION 8 WORKS DEVICE 2 32 34 cus N VIC 33 RHBTHMZ PERCUSSION 2 AND DEv|cE2 INVENTORS JAMES K. PULFER THEODORE H. SHEPERTYCKI TORNEYS.

ELECTRONIC MUSICAL INSTRUMENT WITH A PSEUDORANDOM PULSESEQUENCE GENERATOR BACKGROUND OF THE INVENTION This invention relates to apparatus for automatically producing complex rhythm patterns involving operation of a plurality of percussion devices in a pseudorandom manner.

For some time it has been possible to obtain percussion sounds on a large musical instrument such as a theater organ. These sounds may be artificially generated or may be made with real percussion instruments.

More recently, it has been possible to produce rhythm devices which can control the percussion sound to produce standard musical rhythms such as waltz, fox-trot, etc. Arrangements of this type are disclosed in, for example, the following U.S. Pats:

3.146.290 D.M. Park Aug. 25, I964 3,255,292 D.M. Park June 7, 1966 3,358,068 RJI. Campbell, Jr. Dec. 12, I967 3,383,452 D.M. Park et al. May l4, I968 These patents describe schemes for automatically selecting rhythm instruments such as drum, blocks, cymbals, etc. during prescribed time intervals. None of the devices described in the patents is capable of automatically generating random or pseudorandom rhythm patterns. At most, they are only capable of producing repetitive patterns, which may be manipulated by the artist. The standard rhythm patterns used are quite limited and soon become tiresome.

SUMMARY OF THE INVENTION The present invention provides a rhythm generator which may either lead or follow a performer, and which drives a set of percussion instruments-either real or artificial. Unlike prior art arrangements, the present invention provides rhythm patterns which are pseudorandom, i.e., the repetition period of the pattern is so long compared to the memory of the listener or the duration of a musical selection that it seems to be random. Prior art arrangements can thus be used to provide the normal rhythm accompaniment and the device according to the invention can be used to provide rhythm breaks. The net result is much more pleasant to listen to and approaches the rhythm patterns of a human percussion player. Thus the invention does not supplant the prior art arrangements but adds another dimension to the rhythm possibilities when the musician selects it to perfonn its function. It adds, when selected, a degree of unpredictability to the perfonnance of the rhythm accompaniment which adds considerably to the quality of the resultant performance.

The apparatus according to the invention comprises a source of clock pulses having an output which is applied to a clock input of a pseudorandom pulse sequence generator having a large number of outputs on which appear a large number of different combinations of output pulses, each clock pulse effecting a change in the combination of pulses appearing at the output. The outputs are connected via logic gates to inputs of a plurality of percussion devices whereby the percussion devices are operated in pseudorandom manner at a tempo determined by the source of clock pulses.

Following a brief description of the accompanying drawings, the invention will be described in more detail.

BRIEF DESCRIPTION OF THE DRAWINGS ment using a free-running clock so thatthe musician must follow the percussion devices,

LII

FIG. 3 is a block diagram for explaining a third embodiment having a source of clock pulses which may be synchronized with a musical'instrument playedby a musician,

FIG. 4 is a block diagram of a form of pseudorandom pulse sequence generator which may be used in the present invention, and

FIGS. 5, 6 and 7 are block diagrams showing some possible ways of connecting the outputs of the pseudorandom pulse sequence generator to a plurality of percussion devices.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, a performer (musician) Ill operates a musical instrument II which produces a sound output 13 and also produces clock pulses which are applied to the rhythm box or pseudorandom pulse sequence generator 14 to cause the pattern of output pulses from the rhythm box to change. The musical instrument I! may be an organ and pulse generating means may be incorporated therein or associated therewith so that a pulse is generated each time a pedal is operated by the player. While the output from rhythm box M is shown as a single line in FIG. 1 there are actually many output lines, as mentioned above and as will be explained below in connection with FIG. 4. The output from rhythm box 14 is shown as feeding a box 15 marked percussion which produces a sound output I6 but it should be understood that a plurality of percussion devices will generally be used in practice, e.g. various drums, cymbals, blocks, etc.

The sound outputs 13 and 16 are shown as being fed back to the performer II) which is, of course, what happens, i.e. the performer III hears both sound outputs.

FIG. 2 shows a free-running pseudorandom rhythm box 14 driving percussion devices 15 to produce sound I6. Line 17 indicates that sound 16 is heard by performer 10 who then plays instrument II to produce sound 13. In this arrangement the performer tries to follow the tempo produced by the rhythm box 14' although, of course, this tempo can be set as desired for different musical selections. The source of clock pulses in the FIG. 2 arrangement is not shown separately and may be assumed to be part of the rhythm box."

FIG. 3 shows an arrangement wherein a pulse source on a musical instrument 20 feeds one input of pulse comparison circuitry 21 having another input fed from the output of a source of clock pulses 22 which is also fed to a pseudorandom pulse sequence generator 14 (rhythm box). Pulse comparison circuitry 21 compares the repetition rate of the pulses from pulse source 20 with that of the pulses from the source of clock pulses 22 and if any difference is detected it produces an error signal on line 23 which adjusts the clock pulse frequency to make it agree with the frequency from the pulse source on musical instrument 20. By this means the tempo of the clock pulses is synchronized with the tempo of the musical instrument. Pulse comparison devices are known and one is included in the arrangement described in the US. Pat. 3,243,494 of D. M. Park issued Mar. 29, 1966.

FIG. 4 is a block diagram of a pseudorandom pulse sequence generator suitable for use in the present invention. Other examples are given in an article in Electronic Instrument Digest," May June, 1966 by T. H. Shepertycki entitled Pseudorandom Signals Simplify Telemetry Distortion Measurements. Obviously many types of pseudorandom pulse sequence generators are possible and the operation of the arrangement according to the invention is not dependent on any particular type. The main consideration is that the number of pulse combinations available should be large so that the percussion devices appear to the listener to be operated randomly.

The particular pseudorandom generator shown in FIG. 4 is a 10 stage m-length (maximal length) sequence generator. This type of sequence generator is described in some detail in Chapter III of Shift Register Sequences" by Solomon W. Golomb published by Holden-Day Incorporated, I967, Library of Congress Catalog Card Number 66-17667. Briefly, however, it may be stated that it comprises 10 memory units (flip- .flops)connected together as a storage register. Every clock stage ti, the content of stage 8 is fed into stage 7, and so on. The input to the first flip-flop (stage El) in the register is obtained by combining the outputs of at least two other flip-flops in the register in an exclusive-or adder. Proper choice of these feedback connections will ensure that the lO-bit pattern appearing in the register will not be repeated until 2"-l=2 l==l ,023 clock pulses have been received. A proper feedback connection is shown in FIG. 4 as being from the outputs of stages and 3 via the exclusive OR gate 40.

Outputs 0 to 9 are pulsed each time stages 0 to 9 are turned on by a clock pulse. Output I0 is pulsed each time there is a pulse on output 0 or 3 (but not both) because of the exclusive OR gate 40. Similarly, output 21 is present each time output 4 or output 5 (but not both) is present because of exclusive OR gate il. It should now be obvious how outputs 17 and 25 are derived. It should also be apparent that the remaining outputs (not shown) may be derived by further combining the outputs shown, e.g. outputs 2 and 3, outputs 5 and 9, and so on.

While FIG. 4 illustrates an m-length (maximal length) pseudorandom generator it is not essential that the generator be an m-length one; this is, however, to be preferred to secure the maximum randomncss."

The register shown in FIG. 4 can only hold 1,024 distinct patterns. The only state not generated with this configuration is the all lls pattern.

The stages in FiG. 4 are numbered 0 to 9 from left to right although the first stage is stage 9. They could equally well be numbered from right to left.

While the FIG. 4 arrangement uses exclusiveor circuits, other types could use a combination of OR," AND, and perhaps exclusive-or circuits.

The outputs from the pseudorandom pulse sequence generator can be fed to the percussion devices in many ways. For example, individual outputs can be fed to individual percussion devices, or individual outputs can be fed to more than one percussion device or individual outputs can be combined in other OR" or AND-gates and these outputs used to drive one or more percussion devices. Some of these ways are shown in FIGS. 5, 6 and 7.

FIG. 5 shows only 10 of the many outputs from the rhythm box It (pseudorandom pulse sequence generator). Here it is assumed that percussion device I is connected to output 1 of rhythm box It while percussion device 2 is connected to output 9. Percussion device I will play when (and only when) a one is present on output I of rhythm box M and percussion device 2 will play when (and only when) a one" is present on output 9. Since the pulse sequence passing through the rhythm box takes L023 clock pulses to repeat, the sequence of "ones and zcroesf' passing each percussion device appears to be random."

Switching percussion device 1 to another output changes the delay between the pattern followed by devices 1 and 2. In the FIG. 5 arrangement, the delay would be 91=8 units of time, or 8 clock pulses.

Obviously other percussion devices could be connected to the other outputs of the rhythm box 14. However, it would not be practical to connect 1,023 percussion devices to the 1,023 outputs of the rhythm box; hence an arrangement as shown, in part, in FIG. 6 is preferred. Here logic networks 28 and 29 are used to combine several outputs.

Percussion device ll will only operate when the correct pattern of ones and zeroes" appears at outputs 1-4- of the rhythm box I4. Depending on the logic network selected, percussion device I may be operated more often than in the case of FIG. 5 (if the logic network is mostly OR" gates) or more seldom than in the case of FIG. 5 (if the logic network is mostly AND"-gates As an example, percussion device 1 may be made to operate if any only if the number 1,101 appears on outputs I 4. Since the probability of this happening is relatively small, percussion device I would be used only at rare intervals.

It seems reasonable that if many percussion devices are used say 26-that some should repeat fairly often to provide a basic through perhaps irregular beat, while otherssuch as cymbals or cow bells-should only play at rare intervals.

Obviously the logic networks such as 28 and 29 may be made up of any suitable gates such as OR," AND," "EX- CLUSIVE-OR, "NOR," NAND," etc. While FIG. 6 shows only two logic networks, quite a few more will generally be needed, depending on the number of percussion devices used. Also, while FIG. 6 shows four outputs of the rhythm box connected to each logic network this is only exemplary; more or less than four could be used.

FIG. 7 is similar to FIG. 6 but shows some possible logic networks which may be used. Outputs 1 and 2 of rhythm box 14 are connected to AND-gate 32 having its output connected to AND-gate 3d. Outputs 3 and 4 of rhythm box 14 are connected to OR-gate 33 having its output also connected to AND-gate 34. It will readily be seen that percussion device I will be operated it there are ones" on outputs 1 and 2 and 3 or outputs l and 2 and 4. Percussion device 2 will only be operated only if there are "ones" on all of outputs 5, 6, 7 and 8 so that gate 35 is enabled.

It should be apparent from the foregoing that there exist virtually an infinite number of possible ways of connecting the output leads of the rhythm box to the percussion devices.

The invention could be implemented in many different ways --from a simple integrated circuit pseudorandom pulse sequence generator, which would be quite inexpensive, to a general purpose digital computer, which would be completely impractical in most applications.

What we claim as our invention is:

1. Apparatus for operating a plurality of percussion devices in a pseudorandom manner to produce complex rhythm patterns, said apparatus comprising a source of clock pulses having an output connected to a clock input of a pseudorandom pulse sequence generator, said generator comprising a large number of output tenninals and means to produce a different one of a large number of combinations of output pulses on said output terminals in response to each clock pulse, and means connecting said output terminals to inputs of said plurality of percussion devices whereby said percussion devices are operated in pseudorandom manner at a tempo determined by said source of clock pulses, wherein said output terminals are divided into a plurality of groups of output terminals, each of said groups being connected to an associated logic network having an output connected to an associated percussion device, and wherein said pseudorandom pulse sequence generator comprises a plurality of cascaded flip-flops each of which receives said clock pulses so that the contents of each flip flop is shifted into the next adjacent flip-flop, the first of said flip-flops having an input obtained by combining the outputs of at least two other of said flip-flops, the outputs of said flip-flops being fed to an array of exclusive-or circuits to derive further outputs.

2. Apparatus as claimed in claim 1 wherein there are 10 of said flip-flops and 1,023 combinations of output pulses.

3. Apparatus for operating a plurality of percussion devices in a pseudorandom manner to produce complex rhythm patterns, said apparatus comprising a source of clock pulses having an output connected to a clock input of a pseudorandom pulse sequence generator, said generator comprising a large number of output terminals and means to produce a different one of a large number of combinations of output pulses on said output terminals in response to each clock pulse, and means connecting said output terminals to inputs of said plurality of percussion devices whereby said percussion devices are operated in pseudorandom manner at a tempo determined by said source of clock pulses, wherein said output terminals are divided into a plurality of groups of output terminals, each of said groups being connected to an associated logic network having an output connected to an associated percussion device, and wherein a manually actuated pulse source on a musical instrument supplies pulses to one input of pulse comparing circuitry havinga second input connected to the output of said source of clock pulses, said pulse comparing circuitry producing an error voltage at its output if the repetition rate of the manually operated source differs from the repetition rate of the source of clock pulses, the output of the pulse comparing circuitry being connected to a control input of said source of clock pulses, said source of clock pulses being responsive to 5 an error voltage to adjust its pulse repetition rate to reduce the error voltage to zero.

is s v s e

Claims (3)

1. Apparatus for operating a plurality of percussion devices in a pseudorandom manner to produce complex rhythm patterns, said apparatus Comprising a source of clock pulses having an output connected to a clock input of a pseudorandom pulse sequence generator, said generator comprising a large number of output terminals and means to produce a different one of a large number of combinations of output pulses on said output terminals in response to each clock pulse, and means connecting said output terminals to inputs of said plurality of percussion devices whereby said percussion devices are operated in pseudorandom manner at a tempo determined by said source of clock pulses, wherein said output terminals are divided into a plurality of groups of output terminals, each of said groups being connected to an associated logic network having an output connected to an associated percussion device, and wherein said pseudorandom pulse sequence generator comprises a plurality of cascaded flip-flops each of which receives said clock pulses so that the contents of each flip-flop is shifted into the next adjacent flip-flop, the first of said flip-flops having an input obtained by combining the outputs of at least two other of said flip-flops, the outputs of said flip-flops being fed to an array of exclusive-or circuits to derive further outputs.

2. Apparatus as claimed in claim 1 wherein there are 10 of said flip-flops and 1,023 combinations of output pulses.

3. Apparatus for operating a plurality of percussion devices in a pseudorandom manner to produce complex rhythm patterns, said apparatus comprising a source of clock pulses having an output connected to a clock input of a pseudorandom pulse sequence generator, said generator comprising a large number of output terminals and means to produce a different one of a large number of combinations of output pulses on said output terminals in response to each clock pulse, and means connecting said output terminals to inputs of said plurality of percussion devices whereby said percussion devices are operated in pseudorandom manner at a tempo determined by said source of clock pulses, wherein said output terminals are divided into a plurality of groups of output terminals, each of said groups being connected to an associated logic network having an output connected to an associated percussion device, and wherein a manually actuated pulse source on a musical instrument supplies pulses to one input of pulse comparing circuitry having a second input connected to the output of said source of clock pulses, said pulse comparing circuitry producing an error voltage at its output if the repetition rate of the manually operated source differs from the repetition rate of the source of clock pulses, the output of the pulse comparing circuitry being connected to a control input of said source of clock pulses, said source of clock pulses being responsive to an error voltage to adjust its pulse repetition rate to reduce the error voltage to zero.

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