View Full Version : Commodore 64 as a MIDI device

December 9th, 2006, 02:59 PM
I got myself bored again so I went looking for a Commodore 64 MIDI interface. I found schematics for a Passport compatible interface, plus some software that will convert a C64 into a MIDI slave device.

Looks like fun, just need to get a 2MHz crystal. IMO the SID sounds better than Wavetable.

The schematics are here http://www.zimmers.net/anonftp/pub/cbm/documents/projects/other/C64MIDI-INTERFACE.TXT

and the software for the C64 is here http://www.zimmers.net/anonftp/pub/cbm/c64/audio/players/Midislave-1.1.lnx

It's a LNX file, but Star Commander can open them to transfer the files to disk.

Anyone else used MIDI on the C64?

I'll let you know how my experiment goes.

December 11th, 2006, 01:09 PM
Got it going. It's not nearly as good as I expected it to be. It sometimes misses commands so you get a lost note here or a stuck note there, though it's still quite good for my dodgy techniques.

The schematic for the MIDI interface says the only optoisolator you can use is a PC900. I got it going with a 4N28. Just replace the 270 ohm resistor with a 6k8 one.

Unfortunately I can't record many long tracks in Audacity as it locks up, so I can't sample the different instruments and mix them into a single MP3.

Maybe if I had 16 Commodore's and 16 MIDI interfaces :)

December 11th, 2006, 05:35 PM
I see where your going with this but doesnt it run a little slow to play good music?mp3 you might get away with but im not so sure with cd quality music.

December 12th, 2006, 12:29 PM
This is MIDI not MP3 or WAV.

MIDI is just a string of signals to tell the instruments or synthesizers to turn notes on and off.

Besides, the reason why MP3's have less quality is because they have software compression. This takes an enormous amount of processing power to uncompress. In contrast AIFF or any other CD quality audio is easy on the processor because it lacks compression.

December 12th, 2006, 01:06 PM
There is another guy on this forum who posted his incredibly modded C64 turned into a SID synthesizer, search the threads from the past summer. Of course you also have pure SID based solutions, but that is not the same as connecting a MIDI interface to a C64. Can you program long sequences of arpeggios, pulse modulation, filter programs etc that are used as instruments just like in native SID music programs and trackers?

A bit related, is that Linus Åkesson a couple of years ago transcribed part of Lars-Erik Larsson's classic piece "Förklädd Gud" (translates into "God in Disguise", but I'm not sure if it is known under that name). He used hand-crafted 6502 machine code to sync seven SID chips for a total of 21 channels. As far as I understand, he never got to record the actual SID chips, only through SID emulation.


December 14th, 2006, 01:59 PM
carlsson, This MIDI interface can give music much like that in the link you gave, but the best part is you don't have to destroy your C64 to make it work! :)

Here's a sample. Do we all remember Commander Keen? Good. I chose it because it's the smallest and I'm only on a 256/64k connection. If someone can suggest a good hosting service for MP3's I'd appreciate it.


I created it by playing each instrument separately in Rosegarden (a MIDI based music editor for Linux) and recording them back into Audacity where they were mixed. The only part that isn't from the SID is the drum track because I don't really like SID drums and they're tricky to get going.

I've also done MP3's of the first level of Doom 1, the Lemmings theme, the Space Quest III introduction and the second level of Jazz Jackrabbit (Tubelectic).

December 15th, 2006, 01:21 AM
SID drums can be made very good, but it takes a lot of arpeggio and pulse width patterns, possibly even multi-speed. I don't know how advanced the receiving MIDI software is, what type of instruments you can create for MIDI playback.

December 15th, 2006, 10:56 AM
The software isn't that advanced, I think it was created in a night by some Commodore hackers (Triad). It's got the usual SID settings and a macro function which steps through at the frame rate or a multiple of the frame rate.

By tricky I meant the drums have different sounds for different notes and it's a pain to edit the drum track to get the right instruments out.

December 16th, 2006, 04:30 AM
Ah. It must be a rather early Triad production. At least since the early 1990's, music programs often had the ability to play arpeggios with fixed note frequencies, i.e. independent on the note you ask for. Of course, in the case of MIDI drum tracks, the software would have to translate each pitch into a different instrument instead of just playing one instrument at different pitch.