MIDI files (.mid/.midi) carry note-on/note-off events plus tempo and instrument changes, not audio waveforms. Standardized in 1983 and unchanged in core. Every DAW (Logic, Ableton, FL Studio, Pro Tools, Reaper, GarageBand) reads and writes MIDI. Use it for: scoring, MIDI-controlled hardware (keyboards, drum machines), and the 1990s-era General MIDI ringtones.
How to open
Every DAW (Logic, Ableton, FL Studio, Pro Tools, Reaper, GarageBand, Studio One). MuseScore for notation. VLC and QuickTime can play MIDI through software synth.