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Wavetable-modification instrument and method for generating musical sound
2010-03-12 00:00:00
uniquely identifying each different voice and includes a high-order field for identifying the location within a portion of the memory associated withthe voice identified in the corresponding low-order field.

23. The instrument of claim 22 wherein said generator includes means for decrementing said Write Pointer each time a data value is stored at the location specified by said Write Pointer.

24. The instrument of claim 23 wherein the sampling frequency, fs, is the same for each voice.

25. The instrument of claim 24 including means for providing said data values at a logic cycle frequency which is the number of voices times fs.

26. The instrument of claim 25 wherein the output unit includes a digital-to-analog converter for receiving each new data value for each voice and includes a low pass filter for filtering the analog value from said converter and wherein saidconverter receives a new 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.

27. The instrument of claim 18 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 pitch number N for eachvoice, 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.

28. 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, including a wavetable unit for cyclically storing data values for a delay period defined by a pitchnumber N, including a modifier unit for combining two or more delayed data values from said wavetable unit to form a modified data value, and including selection means for selecting the modified data value or a delayed data value stochastically basedupon a predetermined probability as a stored value stored back into the wavetable unit for subsequent delay by the period N where the stored value forms the output signal,

an output unit responsive to said output signal to produce the musical sound.

29. The instrument of claim 28 wherein said predetermined probability equals unity whereby the stored value is always the modified data value, and has an amplitude yn at a sample time n where yn is given as follows,

where yn-N is the data value output from the wavetable after delay of N and where yn-(N 1) is the data value output from the wavetable after a delay of N 1 and where xn is an input data value at sample time n having a signalamplitude initially loaded into the wavetable.

30. The instrument of claim 29 including means for storing the modified data value, yn, in said memory at a Write Pointer address, including means for storing the data value yn-N in said memory at a Read Pointer address, includingmeans for storing the data value yn-(N 1) in said memory at a Read Pointer 1 address which is offset from said Read Pointer address by 1 and wherein said Write Pointer address and said Read Pointer address are offset by a number of addresses equalto the pitch number N.

31. The instrument of claim 30 wherein said values of xn represent white noise and are given as follows:

where un is determined as 1 or -1 as a function of the output of a random number generator and where A is some amplitude.

32. The instrument of claim 29 including control means for producing the values of yn for the output signal at a sampling frequency, fs, whereby the fundamental frequency of the sound produced for the pitch number N is approximatelyequal to fs /(N 1/2).

33. The instrument of claim 30 including means for storing said Write Pointer address, means for storing the pitch number N as an address offset, means for calculating said Read Pointer address by summing said Write Pointer address and N, andmeans for sequentially changing said Write Pointer address to a new address for each value of yn stored.

34. The instrument of claim 30 including m...

Control system for a musical instrument
2010-03-09 00:00:00
100 exerts pressure on the tactile member 106 until the controller 300 determines in decision state 494 that the musician 100 has sent a clear signal or the controller 300 determines in decision state 498 that the musician 100 has ended the sustained mode of operation.

While the system 104 is in the sustained mode of operation, the musician 100 can halt the sustained or latched volume characteristic by depressing the tactile member 106 (FIGS. 1 and 2) in such a way that the controller 300 is commanded to end the sustained volume characteristic. In the preferred embodiment, the musician 100 can send the clear signal by exerting 51% of the pressure on the tactile member 106 corresponding to the latched volume characteristic. This results in the controller 300 sending a signal in state 496 to the signal modifier 336 to return the volume characteristic to the pre-set volume characteristic.

Alternatively, the controller 300 leaves the sustained mode of operation in response to determining in decision state 498 that the musician 100 has selected a different mode of operation or has turned the system 104 off. Hence, the control system 104 allows the musician 100 to vary the volume characteristic of an audio signal produced by the musical instrument, and also to sustain this volume at a set level, without removing his hands from the musical instrument.

FIG. 9 is a flow chart which illustrates the operation of the control system 104 as it performs the tremolo operation function 454. From a start state 510, the controller 300 initially recalls the selected frequency preset characteristic in state 512. As will be described hereinbelow, the musician 100 can preset up to three separate tremolo frequency characteristic values when programming the tremolo frequency characteristic. Subsequently, the musician 100 can then select these preset values by depressing the tremolo speed button 218 (FIG. 4) one, two or three times. Depending upon the number of times the musician 100 has depressed the frequency select button 218, the controller 300 recalls the appropriate frequency characteristic from the memory 330 and then sends an appropriate signal in state 514 to the audio signal modifier 336 (FIG. 5).

Similarly, in state 516, the controller 300 recalls out of the memory 330 the preset amplitude, i.e., volume, corresponding to the number of times that the musician has depressed the tremolo depth switch 220. As will be described in greater detail below, the musician can also program up to three separate amplitudes for the tremolo characteristic to be applied to the audio signal. Once the controller 300 has recalled the preset amplitude for the tremolo characteristic, it then sends in state 520 an appropriate signal to the signal modifier 336.

Hence, in the tremolo operation function 454, the audio signal produced by the musical instrument 102 is modified by a tremolo characteristic that can be preprogrammed by the operator. The tremolo characteristic is comprised of one of three amplitude characteristics and one of three frequency characteristics that were preset by the musician 100 and then selected while the musician 100 plays the instrument 102.

The controller 300 then determines in decision state 522 whether pressure is being applied to the tactile member 106. If pressure is being applied, the frequency component of the tremolo characteristic is adjusted in state 524 to an extent corresponding to the amount of pressure exerted on the tactile member 106. Hence, the musician 100 can control the frequency component of the tremolo characteristic by manipulating the tactile member 106. This allows the musician to dynamically vary the audio signal produced by the musical instrument 102 while playing the instrument.

The controller 300 also determines in decision state 526 whether the musician 100 has selected a new frequency preset while playing the instrument. The musician 100 can select a different frequency preset while playing the instrument 102 by depressing the tremolo speed button 218 (FIG. 4). This causes the controller 300 to recall the preset frequency component value, corresponding to the new position of the button 218, and send an appropriate signal in state 530 to the signal modifier 336 to thereby change the frequency component of the tremolo characteristic being applied to the audio signal.

Similarly, the controller 300 also determines in decision state 532 whether the musician 100 has selected a new amplitude preset while playing the instrument 102 by depressing the tremolo depth button 220 (FIG. 4). If the musician 100 has selected a new amplitude preset value, the controller 300 recalls the corresponding preset value from the memory 330 and sends an appropriate signal in state 534 to the signal modifier 336 to change the amplitude component of the tremolo characteristic being applied to the audio signal produced by the musical instrument 102.

The controller 300 then determines in decision state 536 whether the tremolo operation function 454 has ended. The tremolo operation ends and the controller enters an end state 540, when the musician 100 selects a different operating mode for the system 104 or turns the system 104 off. Otherwise, the controller 300 returns to decision state 522 to loop through states 522-536 in the previously described fashion. The controller 300 thus can apply a tremolo characteristic to the audio signal produced by the musical instrument that can be varied by the musician changing to different present frequencies and amplitudes using the buttons 218 and 220 (FIG. 4) or by dynamically varying the frequency using the tactile member 106 (FIG. 1).

The foregoing description has described how the controller 300 operates when the musician 100 is playing a musical instrument 102. The musician 100 can vary the volume characteristic of an audio signal produced by the musical instrument and can also apply a tremolo characteristic wherein the components of the tremolo characteristic can be selected from a plurality of preset or prerecorded components. Hence, in operation, the control system 104 of the preferred embodiment significantly enhances the ability of the musician 100 to easily change the audio signal produced by the musical instrument 102.

FIGS. 10-12 are f...