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From: AABENSON@MTUS5.BITNET
Newsgroups: comp.sys.apple2
Subject: Re: GS Sound
Message-ID: <91011.221055AABENSON@MTUS5.BITNET>
Date: 12 Jan 91 03:10:55 GMT
References: <6826@crash.cts.com> <91010.155439AABENSON@MTUS5.BITNET>
 <1991Jan11.191806.27162@en.ecn.purdue.edu>
Organization: Computing Technology Services, Michigan Technological Univ.
Lines: 34

Okay, last time.  This is how sound goes on the IIgs:
<1> First, you choose a VOICE number (a voice is a paired set of oscillators)
   that you want to play your sound with.
<2> Then, you can ALSO choose which CHANNEL this voice goes out.  Unlike
  most stereos, which have TWO output CHANNELS (left and right), the Ensoniq
  chip in the GS actually supports SIXTEEN.  These are not the same as VOICES
  or as OSCILLATORS (half-voices).  Let's try it this way:  ANY of the 32
  oscillators can play on any of the sixteen different channels -- except
  for the fact that the IIgs hardware only multiplexes up 8 of them, therefore,
  only EIGHT channels are supported.  So, what you end up with is "each of
  the 32 oscillators can play through any of the 8 output channels.
  Think of this like your stereo (sorta).  You have several sources of sound.
  An AM radio, FM radio, turntable, and a CD player (if you're lucky) -- think
  of these as your oscillators -- each of them is capable of making it's own
  distinct sound, and with the proper mixing equipment, all at the same
  time.  Now, you have these 32 oscillators (AM, FM, cassette, etc..) going
  into your mixing board.  BUT, this mixing board has EIGHT output channels
  on it, so you can make ANY of your sound inputs (oscillators/voices/tape-
  decks) go to any one of EIGHT different places.  Just because you label
  your CD player "input device #2" (or voice #2, or oscillator #2) doesn't
  mean that it HAS to go to "output #2" -- it can go to any of the eight.

  Anyway, what I was trying to say way back when, was that currently, all of
  the "Stereo cards" for the IIgs just take all of the even numbered channels
  (0, 2, 4, and 6) and send them to one side (left?), and all the odd ones to
  (1,3,5, and 7) to the other (right?) side.  This way, since you don't always
  get to choose which voices you want to play the sounds with, you can still
  control which side the output goes to.


I hope this helps a little --- if not, somebody email me at the address below,
and I'll try real real super-duper hard to explain it.

- Andrew.  (aabenson@balance.cs.mtu.edu     or     aabenson@mtu.edu)