MIDIbox SID synthesizer is a project that uses the classic SID (Sound Interface Device) soundchip from the Commodore C64 personal computer under control of the Midibox as standalone Synthesizer.
For specific info on user created designs, please check the MB-6582,sammichSID,and fnpSID pages.
Info on ucapps.de
General info on the WIKI
PSU Photo Blog
great photo blog about how to canibalize the C64 power supply for MIDIbox SID