[jeffwass]

One more blurb from me :

Check out PAIA Electronics http://www.paia.com

They make DIY audio kits. I built their Fatman synthesiser years ago after graduating university. It sounds great and may give you ideas both on audio generation and midi decoding. It uses an embedded CPU to decode the Midi, and output a voltage linear to the key's pitch. Then has the oscillators (two), filters, low-frequency oscillators, and envelope control. It's a kit you put together, so they give you all the parts. But also they give you schematics. And it could give you some ideas and also a starting place to mod it up yourself. (I had ideas to expound on but never got around to implementing).