A MIDI file is a small file that stores what to play instead of the sound itself. It holds a list of notes, when each one starts, how long it lasts and how hard it was hit. MIDI stands for Musical Instrument Digital Interface, and a program, keyboard or synth turns the list back into sound. If you have a recording and want the notes, the MP3 to MIDI converter does that in your browser.
What does MIDI stand for?
MIDI stands for Musical Instrument Digital Interface. It was introduced in the early 1980s as a standard way for electronic instruments from different makers to talk to each other. Before that, a keyboard from one company could not reliably control a synth from another. Once MIDI existed, you could plug one into the other and play both from a single keyboard.
MIDI is a language, not a type of sound. The same message can be sent over a cable, over USB, or saved to disk as a file.
What is inside a MIDI file?
A standard MIDI file, which usually ends in .mid, is a timeline of events. The main things it can contain:
- Notes. Which key was pressed, as a number from 0 to 127. Middle C is 60.
- Timing. When each note starts and stops, measured against the tempo.
- Velocity. How hard the key was struck, from 0 to 127. Higher velocity usually means a louder, brighter note.
- Tempo and time signature. The speed in beats per minute and the meter, such as 4/4.
- Program numbers. A number that asks the player for a particular instrument. General MIDI defines 128 of them, so number 1 is meant to be a piano on any compatible device.
- Channels. Sixteen per port, so one file can carry a drum part, a bass part and a melody at once.
- Controllers. Extra data such as sustain pedal, volume and pitch bend.
None of this is audio. There are no waveforms in the file. That is why a MIDI file of a full song can be only a few kilobytes.
MIDI vs MP3 vs WAV
| MIDI (.mid) | WAV | MP3 | |
|---|---|---|---|
| What it stores | Note events and settings | The recorded sound, uncompressed | The recorded sound, compressed |
| Sounds like | Whatever instrument you assign | Exactly what was recorded | Close to what was recorded |
| File size | Very small | Large | Medium |
| Can you change the notes? | Yes, one at a time | Not easily | Not easily |
| Can you change the instrument? | Yes, instantly | No | No |
| Contains vocals or lyrics sung | No | Yes | Yes |
Think of a MIDI file as sheet music a machine can read, and WAV and MP3 as photographs of a performance. You can rewrite sheet music. You cannot easily rewrite a photograph.
What people use MIDI files for
- Music production. Producers drop a MIDI file onto a track in a DAW such as Ableton, Logic, FL Studio, GarageBand, Cubase or Reaper, pick a synth or sampled instrument, and edit the notes in a piano roll.
- Keyboards and controllers. A MIDI keyboard sends note data to your computer or to other gear. The keys make no sound on their own.
- Learning and practice. A MIDI version of a piece can be slowed down, transposed or played one hand at a time.
- Sheet music. Notation software can open a MIDI file and show the notes as a score. The result usually needs cleaning up, because rhythm and spelling are guessed.
- Game and ringtone music. Because the files are tiny, older games and phones used MIDI for music. The result depends on the sounds of the device that plays it.
How to get a MIDI file from a recording
You can only turn a recording into notes by estimating which pitches are sounding. This is called audio to MIDI, or transcription.
- Open Audio to MIDI. It also works for MP3 files, and there is a dedicated page for WAV files.
- Load a file, or press Record and sing, hum or play.
- Choose what the recording is: vocals or humming, piano or keys, guitar, bass or a full song.
- Press Convert to MIDI, listen to the result against the original, and adjust the settings if the notes look wrong.
- Download the .mid file and drag it into your DAW.
The conversion is free, needs no sign-up and runs in your browser, so the recording is not uploaded.
What to expect and where it falls short
Audio to MIDI works best on one clear instrument or voice at a time. A hummed melody, a bass line or a solo piano usually turns out well. A whole band in one file produces many extra notes, because the converter hears every sound as a possible note.
If you have a full song, separate the part you want first. The home page stem splitter can pull out vocals, bass and more, the Piano Extractor isolates keys, and the every-instrument splitter goes further. Then convert that single part.
Other limits are worth knowing:
- Drums are hard to turn into useful notes, since they are noise rather than pitch.
- Fast runs, very quiet notes and heavy reverb can cause wrong or missing notes.
- The file carries no tone. A MIDI file of a guitar part sounds like whatever instrument you assign to it.
- You will usually fix a few notes by hand.
FAQ
What does MIDI stand for?
Musical Instrument Digital Interface. It is a standard for sending note and control data between instruments, computers and software.
Can you play a MIDI file by itself?
Not without something to make the sound. A MIDI file needs a synth, a sampled instrument or a sound bank. Many computers have a basic one built in, but a DAW with a good instrument sounds far better.
Is a MIDI file the same as an MP3?
No. An MP3 is recorded sound. A MIDI file is a set of instructions for playing notes. You cannot change the instrument in an MP3, but you can in a MIDI file.
What is a MIDI device?
Any piece of equipment that sends or receives MIDI messages: a keyboard, a drum pad, a controller with knobs, a synth, a sound module or an audio interface with MIDI ports.
How do I make a MIDI file from a song?
Convert the audio with Audio to MIDI or MP3 to MIDI, and for a full mix, split out the instrument you want first so the notes come out cleaner.