# US 4,144,790 A · Choral generator

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- Number: US 4,144,790 A
- Document ID: US4144790A
- Status: Granted
- Kind: A
- Application number: 05/768,600
- Filed: 1977-02-14
- Granted: 1979-03-20
- Earliest claimed: 1977-02-14
- Assignees: ARP Instruments, Inc.
- Inventors: Michael A. Suchoff
- Web page: https://patentgrep.com/patent/US4144790A

## CPC

- G10H 1/10: for obtaining chorus, celeste or ensemble effects (continuous modulation G10H1/043)
- G10H 1/0091: {Means for obtaining special acoustic effects (combined with modulation G10H1/043)}
- G10H 2210/251: Chorus, i.e. automatic generation of two or more extra voices added to the melody, e.g. by a chorus effect processor or multiple voice harmonizer, to produce a chorus or unison effect, wherein individual sounds from multiple sources with roughly the same timbre converge and are perceived as one
- Y10S 84/04: Chorus; ensemble; celeste
- G10H: ELECTROPHONIC MUSICAL INSTRUMENTS; INSTRUMENTS IN WHICH THE TONES ARE GENERATED BY ELECTROMECHANICAL MEANS OR ELECTRONIC GENERATORS, OR IN WHICH THE TONES ARE SYNTHESISED FROM A DATA STORE
- Y10S: TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS

## Abstract

A choral generator is formed from a plurality of delay channels, each including a modulated delay line which non-linearly varies the time delay imparted to a signal passing through it. The outputs of the delay channels are combined with the undelayed audio signal to form a composite output characterized by enhanced musical presence.

## Claims

### Claim 1

In a choral generator having a plurality of delay lines forming a corresponding plurality of delay channels for delaying a signal applied in common thereto, the improvement comprising a separate independed delay modulator for each said delay line, each modulator comprising
A. a clock connected to drive a corresponding one of said delay lines at a rate determined by a control input applied thereto,
B. an oscillator providing a time-varying output signal, and
C. driving means connected to receive said oscillator output signal and providing to the control input of said clock a driving signal that is a non-linear function of said output signal.

### Claim 2 (depends on 1)

A choral generator according to claim 1 in which said driving means comprises means forming an exponential signal generator providing an output exponentially related to the oscillator output.

### Claim 3 (depends on 1)

A choral generator according to claim 1 which includes means for independently varying the frequency of the oscillator output signal to thereby vary the rate at which the time-delay provided by each said delay line is provided.

### Claim 4 (depends on 3)

A choral generator according to claim 3 which includes means for varying the amplitude of the oscillator output signals applied to the driving means to thereby vary the range of time-delays provided by said delay line in response to said driving signal.

### Claim 5 (depends on 2)

A choral generator according to claim 2 which includes frequency-responsive means interposed between said oscillator and said exponential generator for modifying the output of said oscillator as a function of frequency.

### Claim 6 (depends on 5)

A choral generator according to claim 5 in which said frequency responsive means includes a capacitor shunting an increasing portion of the exponential generator input to ground as the frequency of said input increases.

### Claim 7

Sound reproduction apparatus including a plurality of delay lines forming a corresponding plurality of delay channels for independently delaying a common audio signal applied thereto, each delay channel including
A. an oscillator providing a time-varying output for controlling the time delay of said audio signals, said oscillator including
(1) means for varying the frequency of said output to thereby vary the rate at which said time delay is varied, and
(2) means for varying the amplitude of said output to thereby vary the extent to which time delay is varied,
B. an exponential signal generator connected to receive the output of said oscillator and providing a driving signal that is an exponential function of said oscillator output signal, and
C. an analog delay line having a control input connected to receive driving signals from said exponential generator and varying the time-delay of audio input signals applied to said delay line by an amount proportional to said driving signal.

### Claim 8 (depends on 7)

Apparatus according to claim 7 in which said oscillator comprises a low frequency oscillator having an output frequency not greater than approximately 20 Hz.

### Claim 9 (depends on 8)

Apparatus according to claim 8 in which said oscillator includes means to set the output frequency over a range extending from a fraction of a hertz to approximately 20 Hz.

### Claim 10 (depends on 7)

Apparatus according to claim 7 which includes means providing an adjustable bias to said exponential generator to thereby adjust the quiescent frequency driving said delay line.