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Audio Format

MIDI

Musical Instrument Digital Interface

MIDI files are not audio recordings — they're musical instructions. A MIDI file tells synthesizers what notes to play, at what velocity, on what instrument, for how long. The actual sound depends entirely on the synthesizer that plays it. This distinction is fundamental: a MIDI of Beethoven's Fifth Symphony might sound like a grand piano on one system and a toy keyboard on another.

What is MIDI?

MIDI (Musical Instrument Digital Interface) is both a hardware protocol and a file format developed in 1983 by a consortium of electronic instrument manufacturers (Roland, Sequential Circuits, Korg, Yamaha, Oberheim). MIDI was revolutionary: it allowed electronic instruments to talk to each other and to computers, enabling complex music production with synchronized equipment. A MIDI file (.mid or .midi) stores musical events as a sequence of messages: Note On (which note, how hard), Note Off (when the note stops), Program Change (which instrument sound to use), Control Change (volume, pan, sustain pedal, vibrato), Pitch Bend, Tempo changes, and time signatures. MIDI uses 16 channels, each capable of playing a different instrument. Channel 10 is reserved for percussion by convention. MIDI note numbers: 60 = Middle C, each integer = one semitone. MIDI files are tiny: a three-minute song might be 30KB. This made MIDI invaluable in the 1980s-1990s when storage was expensive and internet was slow. MIDI was the dominant music format for computer games (DOS era game music was MIDI), phone ringtones (early mobile phones played MIDI ringtones), and web music (MIDI played in web pages via <embed> tags). MIDI is still essential in music production: all modern DAWs (Logic Pro, Ableton, FL Studio, Pro Tools) use MIDI internally for programming drums, synths, and virtual instruments. MIDI files are the lingua franca of music software interchange.

MIDI pros and cons

Advantages

  • Extremely small file sizes (kilobytes for full songs)
  • Fully editable — change tempo, key, instruments without audio quality loss
  • Universal support in DAWs and music production software
  • Hardware independent — same MIDI plays on any MIDI-capable instrument
  • Precise timing and pitch control
  • Can drive hardware synthesizers and virtual instruments

Limitations

  • Not audio — playback quality entirely depends on the synthesizer
  • Cannot represent human performance nuance without extensive programming
  • Cannot store sample-based audio or vocals
  • Sound varies wildly between different MIDI players
  • Cannot be played directly in most media players (needs a MIDI synthesizer)
  • GM (General MIDI) instrument sounds are often low quality on built-in synths

When should you convert MIDI files?

Convert MIDI to MP3 or WAV when you need a fixed audio recording — for sharing, for use in video, or for playing on devices without MIDI synthesizers. The conversion requires a software synthesizer (like FluidSynth with a SoundFont) to render the MIDI to audio. The quality of the output audio depends entirely on the synthesizer and SoundFont quality. Keep MIDI as the working format for all music composition and production — it's the only format that lets you change key, tempo, and arrangement without any quality loss.

Convert MIDI files

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MIDI FAQ

How do I convert MIDI to MP3?
Converting MIDI to MP3 requires a synthesizer to render the MIDI notes to audio: (1) GarageBand (Mac/iOS, free): File → Open MIDI → play it with a software instrument → Export to MP3. (2) Windows Media Player can play and record MIDI using the system MIDI synth (quality: poor). (3) FluidSynth (free, cross-platform) with a high-quality SoundFont: fluidsynth -ni soundfont.sf2 input.mid -F output.wav && ffmpeg -i output.wav output.mp3. (4) Finale or Sibelius (paid notation software) export to audio with professional-quality virtual instruments.
Why do MIDI files sound different on different computers?
MIDI files only contain musical instructions — the sound comes from the synthesizer that plays them. Different operating systems use different MIDI synthesizers: Windows uses the built-in Microsoft GS Wavetable Synth (basic quality), macOS uses DLSMusicDevice (decent quality), older Windows used FM synthesis (very electronic sound). The same MIDI sounds completely different between these systems. This is why MIDI files from the 1990s sound 'right' on some computers and wrong on others — it depends on which synthesizer they were originally composed for.
What is General MIDI (GM)?
General MIDI is a standard that maps MIDI program numbers to specific instruments — Program 0 is always Acoustic Grand Piano, Program 25 is Acoustic Guitar, Program 57 is Trumpet, etc. 128 instruments are defined in GM. This ensures a MIDI file composed on one GM synthesizer sounds approximately the same on another GM device. GM also defines percussion note numbers: Note 35 = Bass Drum, Note 40 = Snare, Note 49 = Crash Cymbal. GM Level 2 (GM2) added 200 instruments and more percussion sounds.

More formats

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