VIC-20 MIDI Interface and Synth Cartridge Prototype

The VIC-20 was my first computer. You can imagine how close and personal I am with the thing. I do feel that its been unjustly historically overshadowed by the computer that followed it, especially in the audio/music scene.

Viznut and PwP's Robotic Liberation was a real blast and it probably revitalized the scene a bit.

But what we need is a musician friendly way to tackle the beast!
Three years or so ago I requested the help of François Leveillé (aka eslapion) on the Denial forum, a VERY nice electronics guru to help me construct a VIC MIDI Interface like the one HERE . So that I could concentrate on making the 6502 assembly code to read the input MIDI then drive the VIC-I chip. I got the prototype from eslapion, had the core MIDI read code done, but got side tracked by the VIC-I emu in chipsounds and figured I would pursue the project a bit later... that was two years ago.

Early this year Leif Bloomquist wanted to do a similar project, so I just lend him Francois's proto and my preliminary MIDI reading code and hes done VERY WELL with it See and hear it HERE

This is really a prototype, but I believe it is going to transform itself into something that any 8bit musician will not want to miss!

Congrats to Leif for pulling it off! I want serial #00001 ok?


  1. Robotic Liberation is insane. Can chipsounds sound like that?

  2. For the pure VIC tones yes, however for the speech part it requires HUGE sequencer programming. The fake "formants" i suspect is really just switching the different viznut waveforms and pitches in a certain timing.

  3. On closer look speech appears to be a volume/DAC trick.

  4. Some kind of AM?

  5. More like using the volume register as a DAC.

    This particular speech effect is very similar to what has been done for impossible mission and ghostbusters on the C64. which is to play digitized formants and sample and hold certain "steps" in time longer than others.. so its not a true "digi" in the sense that the playback samplerate is not constant.

  6. After even _more_ analysis of the register dumps, its actually a mix of tones and volumes that make the voice. fun fun.

    viznut, you rule.


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