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Revision as of 20:06, 11 September 2008 by Galeandrews (talk | contribs) (expand text and links to MIDI programs and conversion tools)
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MIDI is a compact, notes-based file format widely used for keyboard instruments. It stores how to play the music - which MIDI keys are pressed, and their strength and duration. It is not an audio file format like WAV that stores the full sound of the notes actually being played. Currently, Audacity only has limited support for MIDI.

MIDI and Audacity

Released versions of Audacity can only import MIDI files to view them. Audacity cannot record MIDI input, only audio input.

Development versions of Audacity are slowly adding support for cut and paste MIDI editing and MIDI export, but it is not yet available in mainstream Audacity.

If you want to edit MIDI files in Audacity, you will have to record or convert them to a sampled audio format such as WAV. WAV is the recommended format to use because it is lossless and won't significantly degrade with editing. You can export to a format with smaller file size, such as MP3, after editing.

Converting from MIDI to audio formats

MIDI files can be converted to audio formats either by recording them as they play, or by converting them with another application. Conversion to sampled audio does not retain any of the notation information in the MIDI file, but becomes in essence a recording of that file. How that recording sounds depends on the soundfont or General MIDI banks that are used.

On Windows or Linux, depending on your sound card, you can record the MIDI into Audacity in real time simply by playing it on your computer, for example on Windows Media Player. On OS X you need to use a third-party program recording application such as Soundflower. For more help, see our FAQ on recording streaming audio.

As an alternative, Timidity will convert the MIDI in faster than real time. There is a Windows installer, or you can compile Timidity from source code.

Converting from audio formats to MIDI

Converting in the other direction is a challenging research problem requiring software that can detect the pitch of the notes being played. At present, only single melodic lines can be converted with any degree of accuracy. We'd be very interested in helping a developer who has made progress with such software in helping it reach a wider audience through Audacity. Meantime, here are a few programs you could try:

Programs for working with MIDI

There are many excellent programs for recording and/or editing MIDI files. Many will display the MIDI notes on a musical staff. Here are some recommendations: