EP0124197A2
Expired / Lapsed
EP
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Waveform table modification instrument and method for generating musical sound
Assignee: Leland Stanford Junior University
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Filing: 1984-02-02
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Granted: —
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Expires: 2004-02-02
Abstract
Abstract A musical instrument employing a wavetable-modification method of producing musical sound. A wavetable unit (13) periodically accessed to provide an output signal which determines the musical sound. The output signal from the wavetable unit (13) is modified in a modifier unit (14) and stored back into the wavetable unit (13) as modified data. The modified data, after a delay, is accessed from the wavetable unit (13) and thereby becomes a new output signal. This process is periodically repeated whereby each new output signal is modified and stored back into the wavetable unit (13) to produce rich and natural musical sound.
Inventors
- 👤 Alexander Robert Strong
- 👤 Kevin John Karplus
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-29 15:35
CPC Classifications
G; G10; G10H; G10H7/00; G10H7/02; G10H2250/00; G10H2250/471; G10H2250/475
Claims Analysis
Total Claims: 25
Claim 1
Independent Claim
119 words
A musical instrument for producing musical sound comprising, input means for specifying a musical sound to be generated, wavetable-modification generator means for generating by wavetable modification an output signal representing the musical sound to be produced, and an output unit responsive to said output signal to produce the musical sound, said wavetable modification generator means including a wavetable unit for cyclically storing data values for a delay period N, a modifier unit for combining two or more delayed data values from said wavetable unit to form a modified data value, and means for storing the modified data value back into the wavetable unit for subsequent delay by the period N where the modified data value forms the output signal.
Claim 2
Dependent Claim
119 words
A musical instrument for producing musical sound comprising, input means for specifying a musical sound to be generated, wavetable-modification generator means for generating by wavetable modification an output signal representing the musical sound to be produced, and an output unit responsive to said output signal to produce the musical sound, said wavetable modification generator means including a wavetable unit for cyclically storing data values for a delay period N, a modifier unit for combining two or more delayed data values from said wavetable unit to form a modified data value, and means for storing the modified data value back into the wavetable unit for subsequent delay by the period N where the modified data value forms the output signal.
Claim 3
Dependent Claim
44 words
An instrument according to claim 1 wherein said modifier unit includes an arithmetic unit for summing said two different data values from said wavetable unit and for dividing the summed data value by a number greater than unity to form said modified data value.
Claim 4
Dependent Claim
27 words
An instrument according to claim 2 wherein said number greater than unity is 2 whereby two or more delayed data values from said wavetable unit are averaged.
Claim 5
Dependent Claim
85 words
An instrument according to claim 1, 2 or 3, wherein said modified data value has an amplitude y at a sample time n where y is given as follows: where y n-N is the data value output from the wave- table after delay of N and where y n-(N+1) is the data value output from the wavetable after a delay of N + 1 and where x is an input data value at sample time n having a signal amplitude initially loaded into the wavetable.
Claim 6
Dependent Claim
21 words
An instrument according to claim 4 wherein said output signal is the modified data value having the amplitude y n .
Claim 7
Dependent Claim
74 words
An instrument according to claim 4, wherein said wavetable unit is a random access memory, wherein the modified data value, y n , is stored in said memory at a Write Pointer address and wherein the data value y n-N is stored in said memory at a Read Pointer address, and wherein said Write Pointer address and said Read Pointer address are offset by a number of addresses equal to the delay period N.
Claim 8
Dependent Claim
33 words
An instrument according to claim 6 wherein the data value y n-(N+1) is stored in said memory at a Read Pointer +1 address which is offset from said Read Pointer address by +1.
Claim 9
Dependent Claim
19 words
An instrument according to claim 4 wherein the values of x n stored in said wavetable represent "white noise".
Claim 10
Dependent Claim
42 words
An instrument according to claim 8 wherein said values of x n are given as follows: where u is determined as +1 or -1 as a function n of the output of a random number generator and where A is some amplitude.
Claim 11
Dependent Claim
44 words
An instrument according to claim 4, including control means for producing the values of y n for the output signal at a sampling frequency, f , and wherein the pitch of the fundamental frequency of the sound produced is equal to f s /(N+½).
Claim 12
Dependent Claim
59 words
An instrument according to claim 6, including means for storing said Write Pointer address, means for storing the delay period N as an address offset, means for calculating said Read Pointer address by summing said Write Pointer address and N, and means for sequentially changing said Write Pointer address to a new address for each value of y stored.
Claim 13
Dependent Claim
23 words
An instrument according to claim 11 wherein means for sequentially changing said Write Pointer address includes means for decrementing said Write Pointer address.
Claim 14
Dependent Claim
62 words
An instrument according to claim 6 including means for storing said Write Pointer address, means for storing said Read Pointer address offset by an integer proportioned to N from said Write Pointer address, and means for sequentially changing said Write Pointer address and said Read Pointer address whereby the offset between said Write Pointer address and Read Pointer address remains the same.
Claim 15
Dependent Claim
44 words
An instrument according to any one of the preceding claims wherein said data values are digital and wherein said output unit includes a digital-to-analog converter, a low-pass filter, an amplifier and a speaker for producing the musical sound in response to said output signal.
Claim 16
Dependent Claim
113 words
An instrument according to any one of the preceding claims wherein said wavetable modification generator means includes a wavetable unit for cyclically storing data values for each voice, each having a different delay period N, includes a modifier unit for modifying two or more delayed data values for each voice from said wavetable unit to form a modified data value, for each voice from said wavetable unit to form a modified data value for each voice, and includes means for storing the modified data value for each voice back into the wavetable unit for subsequent delay by the corresponding period N where the modified data value for each voice forms the output signal.
Claim 17
Dependent Claim
75 words
An instrument according to claim 15 including means for storing and updating a Write Pointer each cycle to specify the location in the wavetable at which the modified data value for each voice is to be stored, and including means for storing a delay period N for each voice, and means for determining a Read Pointer for each voice to designate the location of the modified data value for each voice in the wavetable memory.
Claim 18
Dependent Claim
44 words
An instrument according to claim 16 wherein said Write Pointer is common for all of said voices and wherein said generator includes means for adding the delay number N for each voice to the Write Pointer to provide the Read Pointer for each voice.
Claim 19
Dependent Claim
83 words
An instrument according to claim 17 wherein the wavetable is a random access memory, wherein the modified data value for each voice is stored in said memory at a Write Pointer address unique to that corresponding voice and wherein the delayed data values are stored in memory locations determined by a Read Pointer address for each voice and wherein said Write Pointer and Read Pointer addresses for each voice are offset by a number equal to the delay period N for each voice.
Claim 20
Dependent Claim
46 words
An instrument according to claim 18 wherein the Write Pointer address includes a low-order field for uniquely identifying each different voice and includes a high-order field for identifying the location within a portion of the memory associated with the voice identified in the corresponding low-order field.
Claim 21
Dependent Claim
32 words
An instrument according to claim 19 wherein said generator includes means for decrementing said Write Pointer each time a modified data value is stored at the location specified by said Write Pointer.
Claim 22
Dependent Claim
18 words
An instrument according to claim 20 wherein the sampling frequency, f , is the same for each voice.
Claim 23
Dependent Claim
28 words
An instrument according to claim 21 including means for providing said modified data values at a logic cycle frequency which is the number of voices times f .
Claim 24
Dependent Claim
72 words
An instrument according to claim 22 wherein the output unit includes a digital-to-analog converter for receiving each modified data value for each voice and includes a low pass filter for filtering the analog value from said converter and wherein said converter receives a new modified data value at said logic cycle frequency whereby the output from said low pass filter is a signal representing the musical sound for all of the voices.
Claim 25
Dependent Claim
80 words
An instrument according to claim 15 including means for storing a Write Pointer and means for storing a Read Pointer for each voice, said Write Pointer having an address offset from said Read Pointer for each voice by the delay period N for each voice, respectively, and including means for updating both said Write Pointer and said Read Pointer concurrently for each voice whereby the offset N between the Read Pointer and the Write Pointer for each voice is maintained.
References Cited (Backward Citations)
No citation records indexed.
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