Author: (rev. Jim Merritt)
Year: 1987
... discusses multichannel sound with the IIGS Note Synthesizer.
Apple II
Technical Notes
_____________________________________________________________________________
Developer Technical Support
Apple IIGS
#19: Multichannel Output with the Apple IIGS Note Synthesizer
Revised by: Jim Mensch November 1988
Written by: John Worthington & Jim Merritt June 1987
This Technical Note discusses multichannel sound with the IIGS Note
Synthesizer.
_____________________________________________________________________________
It is possible to play multichannel sound using the IIGS Note Synthesizer Tool
Set. The Ensoniq Digital Oscillator Chip (DOC) supports 16 independent output
channels. Since only the low three bits of the output channel number are
available through the IIGS sound expansion connector, multichannel circuitry
may only decode eight output channels (zero through seven). Output channel
eight maps onto channel zero, channel nine onto channel one, etc., and this
mapping continues through all 16 channels.
The setting of the high nibble of the DOCMode byte in a waveform of the
waveList portion of the instrument definition determines the routing of output
from a Note Synthesizer instrument to a particular channel (the actual DOCMode
information is in the low nibble of the DOCMode byte). You may assign each
separate element in a waveList to a different output channel to create
multisampled instruments in which some samples play on the left speaker and
others on the right.
Apple standards require stereo expansion cards to map all even output channels
to the right and odd channels to the left. To be compatible with cards that
decode more than two of the chip's output channels, software should use
channel zero for right and channel one for left. This convention ensures that
output is always positioned properly in the stereo space with channel zero
information going to the right front and channel one information going to the
left front.
Further Reference
o Apple IIGS Toolbox Reference, Volume 2
o Apple IIGS Toolbox Reference Update