0.1
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Okay...this is the debug version...it has problems:
doesn't play on channels 1,2,3...4 doesn't stop playing.
the volume is wrong.  it looks like the voice_data
structures are getting mangled somehow.  I just thought
I'd check it in at this point because all of the code is
written.

0.3
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voice_data structures have been verified to be operating correctly.
(this was done using midiout with midi-ox)

noteoff seems to be zeroing the velocity properly following a
note off message.

sample start addresses are properly chosen based on channel number.
deltas are being properly chosen based on note number.
velocities are being properly multiplied.
max d/a output total really does equal about 0x7fff


0.4
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I have no idea what the state is right now!  mostly...random bugs I'm
trying to fix, arg!  Just releasing this for Brian to work on!