.midi File Extension

What kind of file is a .midi?

A .midi file is normally a Standard MIDI File (SMF). Instead of recorded sound, it contains timed performance instructions such as notes, channels, tempo changes, controller movements, track names, and lyrics. A synthesizer, sampler, or virtual instrument turns those events into sound, so playback can vary between systems.¹

The commonly used MIME types are audio/midi and audio/x-midi, although neither currently appears as a registered standards-tree type in IANA's audio registry.² A normal SMF starts with the ASCII signature MThd, or hexadecimal bytes 4D 54 68 64, and its track chunks start with MTrk.³ Check this structure when the suffix might be misleading.

How do I open a .midi on my computer?

Use a digital audio workstation, notation editor, sequencer, or dedicated MIDI player with access to a synthesizer:

• On macOS, Logic Pro can open and import Standard MIDI Files, create software-instrument tracks, and export SMF formats 0 and 1.⁴
• On Windows, macOS, and Linux, MuseScore can import a Standard MIDI File for notation and editing.
• Ableton Live on Windows and macOS imports SMF formats 0, 1, and 2, but its documentation says to rename .midi to .mid before importing.⁵

A browser audio control usually cannot play the file because browsers do not provide a built-in SMF synthesizer or sound bank. The Web MIDI API connects web apps to MIDI devices; it is not itself a file player.⁶

Poly support for .midi

Poly recognizes .midi filenames as audio, stores and syncs the files, and makes their names and basic properties searchable. Recognized files open in the audio-player interface, but standard browser playback does not synthesize their event data, so preview is limited.

Poly does not currently extract MIDI events, track text, lyrics, duration, or audio-similarity data. It does not create a transcript or make the musical content available to the Poly agent. Download the file to use it in a MIDI-capable application. For reliable playback or audio-aware features, render a separate audio copy and retain the .midi original as editable performance data.

History of .midi

MIDI 1.0 appeared in 1983 as a way for electronic instruments to exchange performance messages. Sequencers still stored projects in incompatible formats, so the MIDI Manufacturers Association adopted the Standard MIDI File format in 1988 to make time-stamped performances portable.³⁷

The four-character .midi suffix describes the same SMF convention commonly stored as .mid. An SMF header declares one of three organizations: format 0 has one track, format 1 has simultaneous tracks, and the uncommon format 2 contains independent sequences.⁵

Working with .midi and alternatives

Rendering MIDI is more than changing containers. The result depends on the chosen instruments, sound bank, effects, tempo handling, controllers, and System Exclusive support. Listen to the complete output before relying on it. Converting recorded audio back to MIDI is a transcription task and cannot recover the original events exactly.