The Roland PG1000 was modified with a reprogrammed EPROM memory. Each of its 56 sliders (plus 8 additional external control voltages) can be set from the front panel pushbuttons and LCD screen to put out one of several MIDI signals: any MIDI Control, NoteOn/NoteOff, Program Change, NoteOn with Aftertouch, Channel Pressure, Pitch Wheel.
A Forth Programming system was set up in the Rom Memory and the actual reprogramming was then a combination of Forth subroutines and Assembly Code subroutines.
A complete description of the program is contained in downloadable PDF files. Also available for download is the actual code for burning onto a 27C128 EPROM chip.