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Conference napalm::commusic_v1

Title:	* * Computer Music, MIDI, and Related Topics * *
Notice:	Conference has been write-locked. Use new version.
Moderator:	DYPSS1::SCHAFER

Created:	Thu Feb 20 1986
Last Modified:	Mon Aug 29 1994
Last Successful Update:	Fri Jun 06 1997
Number of topics:	2852
Total number of notes:	33157

1599.0. "LA synthesis explanation wanted, please!" by TOOK::DDS_SEC (What, are you silly?) Thu Aug 04 1988 17:48

	No, no, not another novice question!

	Here goes:  Can anyone point to a note or explain right HERE exactly
or semi-exactly how LA synthesis works?  I tried dir/key=LA and all there was
was an announcement of the D1(1)0.  Help!

�

T.R	Title	User	Personal Name	Date	Lines
1599.1	LA overview	SUBSYS::ORIN	AMIGA te amo	`Fri Aug 05 1988 00:58`	38
	The D50 architecture - The Roland D50, D10, D20, D110, D550 all rely upon a new custom designed IC know as the 'LA CHIP'. LA stands for Linear Arithmetic synthesis. The sound is entirely computer generated. There are four distinct sections to the D50/D550... digital synthesizer digital equalizer digital chorus digital reverb Each patch is a combination of one to four sounds (called partials). These partials can originate from pulse code modulation (PCM) digital sample waveforms or "conventional" sawtooth, square wave, or triangle waveforms. Two partials form a "tone", two tones form a "patch". The partials can be mixed directly, or mixed with a ring modulated version to form the tone "structure". The ring modulator "multiplies" the two partial sounds, forming complicated harmonics. A wave generator section is used to control the pitch and waveform. A time variant filter (TVF) is used as a low pass filter to cut off the higher frequency harmonics. A time variant amplifier (TVA) is used to control the volume of the partial. An envelope generator is used to control the pitch, timbre and volume of each partial. A low frequency oscillator (LFO) is used for pitch, pulse width, cutoff frequency, or level. This generates vibrato, pulse width modulation (PWM), or tremolo effects. The equalizer (EQ), chorus, and reverb sections are used to provide digital signal processing (DSP). Finally, the mixed sound can be fed to the stereo outputs in various modes which incorporate the different types of reverb. This is a very brief description. Hope it helps. dave
1599.2	Like SQ-80, but different?	CTHULU::YERAZUNIS	Why are so few of us left healthy, active, and without personali	`Fri Aug 05 1988 10:43`	5
	So, it looks a _lot_ like a subtractive wavetable synth, except that the modulation paths are fixed and there is a digital EQ and a digital reverb at the end of the "pipe". Do I have that right?
1599.3	hybrid	SUBSYS::ORIN	AMIGA te amo	`Fri Aug 05 1988 12:15`	10
	I would say it is more of a hybrid of additive, subtractive, and wavetable synthesis. That is why the sounds are so "fat". There are so many ways to combine various partials and waveforms, filtering and modulation. It takes about 30 seconds to get a completely original sound, and could take hours to try the various meaningful permutations of parameters. The COMPARE feature when editing tones is great for checking on what you started out with compared to what you have now. The PG1000 programmer gives you easy access to the myriad of parameters without wading thru the menus. dave