A demo (shortened from "demonstration") is a song or group of songs typically recorded for limited circulation or for reference use, rather than for general public release. A demo is a way for a musician to approximate their ideas in a fixed format, such as cassette tape, compact disc, or digital audio files, and to thereby pass along those ideas to record labels, producers, or other artists.

Demos are typically recorded on relatively crude equipment such as "boom box" cassette recorders, small four- or eight-track machines, or on personal computers with audio recording software. Songwriters' and publishers' demos are recorded with minimal instrumentation, usually just an acoustic guitar or piano and the vocals.