A .SID file, colloquially known as 'a SID', is a sound data file not only containing the note patterns, but also the 6502 program code - often called a 'player' - needed to replay the music on the SID. All actual sound is produced by the SID chip, or a software emulator that emulates the SID chip. The High Voltage SID Collection contains over 45,000 SID tunes. The SID files have the MIME media type audio/prs.sid.

The SID file format is not a native format used on the Commodore 64 or 128, but a format specifically created for emulator-assisted music players such as PlaySID , Sidplay and JSidplay2. However, there are loaders like RealSIDPlay and converters such as PSID64 that make it possible to play a substantial portion of SID files on original Commodore computers.

MOD is a computer file format used primarily to represent music, and was the first module file format. MOD files use the ".MOD" file extension, except on the Amiga where the original trackers instead use a "mod." prefix scheme, e.g. "mod.echoing". A MOD file contains a set of instruments in the form of samples, a number of patterns indicating how and when the samples are to be played, and a list of what patterns to play in what order.