Eight bit computer hardware/software

[Grant Richter]

I am wondering if there are any cool sound peripherals
or voice synthesizers for eight bit computers 
worth keeping an eye out for at resale shops.
I know someone did something interesting with the
Commodore SID chip (Sidstation). I thought I would
start a list of interesting items to watch for in the junk
stores.

First would be the Commodore 64s with the SID chip.
Both Atari's and Commodores had MIDI interfaces
with sequencer packages.
The TI/99 had a Voice Synthesizer peripheral
One of the Apple computers had the same sound chip
and the Mirage and ESQ-1 (DOC-1 Chip)
Mountain Valley Computers had a music synthesizer
that plugged into a Apple IIe.
Votrax made a voice synthesizer that plugged into an
Apple IIe
The RCA COSMAC VIP had a four channel music
synthesizer card that attached.

A friend of mine had a multi-channel CV sequencer
program that ran on a KIM-1 using a DAC