File extension
.mid
Standard MIDI File Format
.mid files are Standard MIDI Files: they store sequences of musical performance events — notes, timing, and controls — rather than recorded audio, to be played back by synthesizers or software instruments.
Known meanings
Formats and reference material for .mid
Standard MIDI File Format
Standard MIDI File Format
General MIDI Level 1 Spec.
General MIDI Level 1 Spec.
MIDI Manufacturers Association - the definitive source of MIDI information.
MIDI Manufacturers Association - the definitive source of MIDI information.
Standard MIDI File Format
Standard MIDI File Format
The USENET MIDI Primer (note .KAR files are standard MIDI files)
The USENET MIDI Primer (note .KAR files are standard MIDI files)
MIDI Sample Dump Standard
MIDI Sample Dump Standard
Details
Format notes
Standard MIDI File (SMF)
A Standard MIDI File stores music as a sequence of instructions rather than as
recorded sound. Instead of audio samples, a .mid file contains timed MIDI events
— note-on and note-off, pitch, velocity, program (instrument) changes, controller
movements, and tempo — that a synthesizer, sound module, or software instrument
interprets to produce audio. This makes MIDI files tiny compared with audio
recordings and fully editable at the note level, but it also means the same file
can sound quite different depending on the instruments used to play it.
The format is chunk-based: a header chunk (MThd) specifies the format type and
timing resolution, and one or more track chunks (MTrk) hold the event streams,
each event preceded by a delta-time. There are three format types: type 0 (a single
combined track), type 1 (multiple synchronized tracks, the most common), and type 2
(independent patterns). General MIDI is a companion standard that fixes a common
instrument map so files play consistently across devices. Karaoke .kar files are
Standard MIDI Files with embedded lyrics.
Preservation Notes
MIDI is compact, open, and well documented, making it excellent for preserving the
performance/score data of a piece. The important caveat is that playback depends on
an external sound source (a synthesizer or soundfont), so a faithful rendering
should record or bundle the intended instrument set; the .mid alone captures the
notes, not the timbre. The common media type is audio/midi.
Security Notes
As a chunked binary format with variable-length quantities and length-prefixed tracks, a MIDI parser should validate chunk and event lengths from untrusted files to avoid over-reads.
Further Reading
- MIDI Association (specifications):
https://www.midi.org/specifications