What Is a MIDI File?

This article explains what a MIDI/MID file is, how to open one, and how to convert one to a different file format, including sheet music.

What Is a MIDI File?

A file with the .MID or .MIDI file extension (pronounced as "mid-ee") is a Musical Instrument Digital Interface file.

Unlike regular audio files like MP3s or WAVs, these don't contain actual audio data and are therefore much smaller in size. They instead explain what notes are played, when they're played, and how long or loud each note should be.

Files in this format are basically instructions that explain how the sound should be produced once attached to a playback device or loaded into a particular software program that knows how to interpret the data.

This makes MIDI files perfect for sharing musical information between similar applications and for transferring over low-bandwidth internet connections. The small size also allows for storing on small devices like floppy disks, a common practice in early PC games.

You can read more about this format at the MIDI Association.

How to Play MIDI Files

Open a MIDI file with Windows Media Player, VLC, WildMidi, TiMidity++, NoteWorthy Composer, Synthesia, MuseScore, Amarok, Apple's Logic Pro, and other popular media players. To play one online, try Online Sequencer.

Midi Sheet Music is a portable program (you don't have to install it) that can play the file, too, and it even shows you the sheet music in real time during playback. It also lets you convert it to sheet music that you can print or save to your computer as either a PDF or as multiple PNG images.

Sweet MIDI Player is a MIDI player for iPhone and iPad, but it plays only 75 percent of the file unless you pay. Android users can open MID files with Fun Fun MIDI Player or MIDI Voyager Karaoke Player.

How to Convert a MIDI File

Zamzar is a free online file converter that can convert MIDI to MP3, WAV, AAC, FLAC, OGG, WMA, and a few other audio formats. Other tools work just as well, some of which are in this Best Free Audio Converter Software Programs list.

The Midi Sheet Music program from above can be used to convert the file to sheet music.

Still Can't Open It?

At this point, if you've tried all of the above and none of the websites or programs will open your file, it's important to know that some files share some of the same letters in the file extension even if their formats are unrelated.

In other words, your file might look like it's MIDI or MID when really it's something similar like MD or MII (Wii virtual avatar file).

Another file extension that looks like these is MDI, used for Microsoft Document Imaging files. If you have this file, it won't work with the programs linked above, but instead requires Microsoft Office or MDI2DOC (to convert it to DOC).