MOD is a music module file format that originated on the Commodore Amiga, combining sampled instrument data with pattern-based note sequencing in a single file. It was designed to leverage the Amiga's Paula chip, which could play back four independent 8-bit PCM channels simultaneously via DMA, allowing for rich polyphonic music without consuming significant CPU resources. Popularized by tracker software such as ProTracker, NoiseTracker, and OctaMED, the format became ubiquitous in Amiga games, demos, and the demoscene, offering an efficient alternative to streaming audio by storing note commands and small sample loops rather than full audio recordings.