I first learned about tracker / mod music on my Amiga in the early 1990's. I remember fooling around with Protracker, listening to mods with Intuitracker, and coming to the realization that all those awesome demos, crack intro's and trainers were generally using the same technology to create those iconic soundtracks.

Winding the clock back in time, I've been reconstructing a Commodore 64 ML program I wrote when I was about 15 or 16 that plays a basic beep-beep tune I was developing for a video game. I've recently disassembled my original code, loaded the assembly into CBM .prg Studio and spent some time doing refinement and cleanup. What I discovered along the way, was that my approach was eerily similar to how I now understand trackers to work, and also how I would have expected SID files to work, albeit a much more primitive implementation.

This leads me to wonder about SID files on the C64. Was there a de-facto editor for the C-64? Something that might be considered the definitive tool every crack team's audio-guy reached for to whip up a new tune for their next release? If so, was the file format ever published or documented (by now it must be, right)? And finally, is publicly available assembly available for playback (assuming a C64/SID architecture)?

Applying 20-20 hindsight, it seems a modern developer doing a retro project would expect to simply download the editor, author some awesome music, export the data and spark up some boiler-plate assembler for playback.

Please note, I'm interested in the technology as it existed on an actual C64. I realize there are modern editors that run on Windows and what not, but if it was 1987 and you wanted to make some Chiptunes on your Breadbox, what tools would you reach for?


Brian H kindly pointed me back to this question, which is chuck full of SID file goodness, but doesn't really tell me what the leader of the pack was back in the 80's. It does mention that what I refer to as a tracker/mod were actually called SID files, and that they bundled the playback code with the data into a single file.

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    Does this answer your question? How did C64 games handle music during gameplay?
    – Brian H
    Oct 23, 2020 at 13:26
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    The C64 didn't have capability to play module files, so there were no trackers for the platform. Mods were based on PCM sound samples embedded in the file that the player would mix together at varying rates (frequencies) to produce music. In particular, format was designed around the capabilities and limitations of the Amiga's sound hardware. Even playing one PCM sample at a fixed rate was beyond what the C64 could really do. (Though there we some crude 1-bit effects at the time, and much more recently hackers have found a way to get the SID to output 8-bit samples.)
    – user722
    Oct 23, 2020 at 16:03
  • I missed that question, so thanks for pointing that out to me! (I even commented on it at the time). But while there is a lot of good info there, it's not exactly giving me the info I am looking for. The linked page of editors shows JCH from 1991 and DMC 1993, but I suspected there was some contemporary 1985 to 1988 ish editor that was the go-to choice. I did not know the playback code was bundled into the file itself.
    – Geo...
    Oct 23, 2020 at 16:05
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    @Ross, thanks for the clarification. I understand the SID chip (and 64) was not designed for samples, and only synthesis of sounds (waveform/ADSR.etc). But the principle of how the editors sequence repeating patters of notes, and arrange those patters to create long playing music is the same.
    – Geo...
    Oct 23, 2020 at 16:07
  • Those aren't trackers, which create module files as I described. There were music editors for the C64, including ones that created SID files, which were the defacto music file format for the C64, but SID files aren't "tracker music".
    – user722
    Oct 23, 2020 at 16:09

2 Answers 2


No - at least not in the sense of some shared data structure that different music editors were all capable to work with, as was the case with fx MOD files and derivatives.

C64 music is typically distributed as executables which contain both play routine and music data (cf. also this answer). Many different players and editors exist, some native, some for "cross composing". The music is played by the player software continuously changing the SID chip's parameters.

Composers, or groups, often wrote the play routines themselves and held on to them, and the particulars of a given implementation was often part of the artist's distinctive style. Also, play routines evolved a great deal, everyone trying to get an edge in sound capability, raster time usage or whatever trade-off of the system's constraints were relevant in the context.

There is, however, a pretty standardized meta data header - PSID - that represents the information needed to play the music from emulating music players or for generic front ends on the C64 itself. But this was something that was invented after the fact, when people started building collections and wanting to play the music on other systems as well (fx the tracks you find in collections such as the HVSC are wrapped in this header).

There was not really any single "leader of the pack", but there were a few play routines used by popular and productive composers that you were likely to encounter, such as:

  • Rob Hubbard's
  • Martin Galwin's
  • Matt Gray's
  • 20CC's
  • Vibrants'

And also those of some widely available music editors such as:

  • Future Composer
  • Music Assembler
  • DMC
  • I'd say those executables were the defacto format.
    – user722
    Oct 23, 2020 at 16:25
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    Amiga MOD music is merely declarative, SID music is procedural and requires a full-blown emulator of the SID chip or virtual machine to play back nowadays. Oct 24, 2020 at 2:31
  • @Retrograde, good info. I think some of my confusion was due to the fact that technically speaking, trackers work with samples and author mod files, but they also sequence note patterns in a unique way (compared to say, a music score like Deluxe Music). Many of the editors for the C64 (like FutureComposer, SID DuzzIt, Cybertracker, etc) use the same approach to editing the note patterns, with the major difference being note synthesis via the SID chip vs sample playback. These programs are often incorrectly mis-catagorized as trackers (which is a mistake I also made in my initial post).
    – Geo...
    Oct 24, 2020 at 11:49
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    @scrollbear: the big difference isn't that they require full-blown SID emulation (that is expected, since the sound needs to be synthesized by something), but that they ALSO require emulation of the 6502 CPU.
    – Cactus
    Apr 8, 2021 at 6:44
  • @Cactus right, but then there might also be Amiga music that doesn't work with a MOD player if it uses uncommon effects/additions/modifications calculated by the Motorola CPU. Sound chips were used back then also because it's difficult to get timing right if other tasks have to run too at the same time, so they also help to parallelize. I didn't run the numbers but I'd guess ~most SID tunes ought to use a standard/predictable playback routine controlled by the 6502, so not that much different to the Amiga setup. Apr 17, 2021 at 15:02

Today maybe GoatTracker and its stereo release.

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