found a few more nice Open Source voice chips..
PreenFM
https://sites.google.com/site/preenfm/This is like a DX7. 9 algo's, 6 OP's. Up to 8 voices.. only 4 if you use up all 6 OP's.
Mini Maple Chip board is a little high at $35, but you get up to 8 voices with just one chip/board. Appears to come with USB port built in.
Program in C++, open source. Midi ready.
Rockit
http://hackmeopen.com/rockit-build-info/This is the one I like best of the two. Another wavetable synth. Chip is $8 at Digikey.. $15 preprogrammed from the hackme store.
Written in standard C, full schematics seem to indicate the use of 3 digital pots to control VCA/VCF's.
Has MIDI control of all the parameters... I may be wrong, but it shouldnt be too difficult to change the code so the HAWK sends it note messages and other parameter controls.
Looks like he did a nice job of commenting all the code out.. even a n00b like me can follow fairly close to what's going on.
There's been some mention of a simple wavetable sample editor for it as well.. so you can even "scribble" your own waves up.
Only two OSC's.. but they can morph 2 waves, etc.
Gordon, isnt the ATmega644 the same mfr as the AVR chips you mentioned using?
-Blaine