Music – Instruments – Electrical musical tone generation
Utility Patent
1998-01-27
2001-01-02
Donels, Jeffrey (Department: 2837)
Music
Instruments
Electrical musical tone generation
C084S629000, C704S503000
Utility Patent
active
06169240
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a tone generating device and method for performing control to optionally stretch or compress a time-axis length (reproducing time length) of tone waveform data in whole or in part independently of pitch control of the waveform data, to thereby enhance expression and controllability of the tone in the time-axis direction. The present invention is applicable extensively as a tone generating device and method for not only electronic musical instruments but also various other tone or sound generating instruments such as game machines, personal computers and various multimedia equipment.
In the conventionally-known tone generators based on the waveform memory reading method (PCM or Pulse Code Modulation method) which are used in electronic musical instruments and the like, a pitch of each tone waveform to be generated have been controlled by adjusting the rate of the waveform data readout from a waveform memory. More specifically, when sequentially reading out the waveform data with read addresses generated by accumulating so-called “F numbers” (frequency numbers which are constants proportional to a tone pitch frequency), the pitch can be controlled to become higher by increasing the value of the F number and become lower by decreasing the value of the F number. In this case, when a set of waveform data of limited quantity is read out, the tone-reproducing or tone-generating time length of the waveform data would undesirably vary depending on the readout rate of the waveform data (waveform samples). Namely, the tone-generating time length would become shorter as the pitch becomes higher. Thus, the conventional PCM tone generators were not satisfactory in that it could not perform control to freely stretch or compress the time length, i.e., tone-generating time length of the waveform data to be read out from the waveform memory, independently of the pitch.
Further, with these PCM tone generators, it has been conventional to control three different tonal factors: pitch; volume; and color (or timbre), when a user desires to impart particular expression to a tone to be generated (which will be sometimes referred to as “to-be-generated tone”) by applying some modification to the waveform read out from the memory rather than merely generating the read-out waveform directly as a tone. For the tone pitch, a pitch modulation effect, such as a vibrato or attack pitch, is imparted by modulating the waveform data readout rate as necessary. For the tone volume, a tremolo effect or the like is imparted by imparting a volume amplitude envelope, based on a given envelope waveform, to the read-out waveform data or by periodically modulating the volume amplitude of the read-out waveform data. Further, for the tone color, suitable tone color control is performed by subjecting the read-out waveform data to a filtering process. As noted above, the known tone controlling technique for imparting expression to a to-be-generated tone comprises performing some control on the three major tonal factors: pitch; volume; and color. However, there has never been proposed so far an idea of controlling waveform data of a to-be-generated tone along the time-axis to thereby impart expression to the to-be-generated tone for enhanced tonal expression and controllability.
Further, quality of natural instrument tones can not be easily approximated by the above-mentioned external control of the three tonal factors in the PCM tone generator: variation of the readout rate; control of the volume amplitude of the read output; and filtering of the tone color. Thus, to enhance the quality of tones generated by the PCM tone generator, it has been conventional to prestore in the waveform memory plural-cycle waveforms with various modulation effects, such as a vibrato and tremolo, previously imparted thereto so that tones having these modulation effects can be generated, with as good quality as that of natural instrument tones, by just reading out the stored waveforms. However, in the case where the waveform data of tones having modulation effects imparted thereto are read out from the memory, the modulating cycle and modulating time would undesirable vary as the waveform data data readout rate is changed; that is, the modulating cycle, modulating time, etc. could not be controlled independently of the waveform data readout rate, i.e, tone pitch.
Further, although the PCM tone generators can prestore, in the waveform memory, high-quality waveform data corresponding to desired tonal effects and characteristics by sampling them directly from a natural musical instrument, they preset the problem in that if they are read out with the pitch controlled (i.e., with the readout rate varied), the time axis of a generated tone would vary in response to the varied readout rate. Such a disadvantage may be avoided by preventing variation of the readout rate, but where a multiplicity of pitches are to be reproduced precisely in cents as in the case of musical instrument tones, an extremely great memory capacity would be required if a multiplicity of sorts (sets) of plural-cycle waveform data having various effects imparted thereto are prestored for each of the pitches. Thus, this approach is very impractical.
Further, in the field of voice processing, the PICOLA method is currently known as one of the speech speed converting techniques. For example, when applied to a situation where waveform blocks A, B, C, D and E for five wave cycles are read out in the mentioned order at a predetermined reproducing sampling frequency to output a voice waveform, the PICOLA method may use, for the first cycle, a waveform obtained by adding together a waveform for fading out block A and another waveform for fading in block B and then output blocks C, D and E for the second to fourth cycles. In this way, without varying the predetermined reproducing sampling frequency, the PICOLA method can output the waveform, originally having a total time length of five cycles, with the time axis compressed to just four cycles. When applied to another situation where waveform blocks A, B and C for three cycles are read out in the mentioned order at a predetermined reproducing sampling frequency to output a voice waveform and if time-length expansion or stretch is desired, the PICOLA method may use block A for the first cycle, then use, for the second cycle, a waveform obtained by adding together a waveform for fading out block A and another waveform for fading in block B, and then output blocks B and C for the third and fourth cycles. In this way, without varying the predetermined reproducing sampling frequency, the PICOLA method can output the waveform, originally having a total time length of three cycles, with the time length expanded or stretched to four cycles. However, this speech speed converting technique can merely read out the recorded voice signal at the predetermined reproducing sampling frequency and is never intended for variably reading the voice signal at an optional pitch (tone pitch). In other words, the conventional technique provides no countermeasures or solution to the above-mentioned problem.
As set forth above, the conventional waveform-memory-based tone generators for electronic musical instruments have the problem that the time length of the read-out waveform data is invariably determined depending on the readout rate and hence can not be stretched and compressed freely. Further, the conventional voice processing technology is in no way intended for precise pitch control in cents, and it is difficult to apply such voice processing technology directly to the waveform-memory tone generators.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a technique suitably applicable to a tone generator based on waveform data readout from a waveform memory, which can perform optional variable control of the data readout rate (pitch) and also perform control for optionally stretching and compressing the waveform data along a time axis independently of the readout rat
Donels Jeffrey
Morrison & Foerster
Yamaha Corporation
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