Midi is a system for describing musical events to be played by a synthesizer, and it is found in almost all electronic musical instruments and music software.

A Brief History

Midi originally appeared in piano keyboards in the 1980's, where it could be used to record the notes in a passage of music for subsequent playback, similar to the old pianola concept.  Keyboards could also be connected together to control each other using Midi.

Since the rise of the multimedia computer in the 1990's, it has become much more useful as a language in which a whole song can be described, stored and replayed by increasingly sophisticated software.

For playback, a computer can still be connected to an external piano keyboard or sound module, but much more common now is to use an internal Midi sound card or software synthesizer on the computer itself.

Midi vs Audio

Midi is a set of instructions on how to play a song, but it is not the audio sound of the song itself, such as you might find on a CD.  In this way it is like a screenplay, rather than the movie made from the screenplay.

The audio that you hear when you play Midi is actually being generated by the synthesizer (sound card, sound module, piano keyboard, etc).  This has several implications.

1. Midi is a very compact way of describing music, because it is a series of short instructions rather than the detailed waveform of the music itself.  Three minutes of music stored in a Midi file might use 70 kB compared to 30 MB for a Wave file or 3 MB for a compressed Mp3 file.

2. Midi music can be changed easily by simply editing the properties of the musical events.  Despite recent advances in audio processing software, waveform audio is largely fixed, especially when several tracks have been mixed together.

3. Midi can be directly translated into staff notation, which is also based on a description of the events and timing in a piece of music.

4. The sound of Midi playback will vary depending on the sound generator.  It will be recognizably the same song, but some devices will sound dinky, while others will sound awesome.  Exact tones, volume balances and effects may also vary.

For these reasons, Midi is ideally suited to the creation, arrangement and communication of music by musicians.  It gives a musician access to the sounds of instruments they don't own or can't play, it can be easily worked with and changed, and it can be readily printed as staff notation.

But the final step of music production will almost always involve rendering the Midi events into a wave format so that the exact sound can be captured, audio effects can be applied, and acoustic instruments and vocals can be added.

Midi in Songtrix

Musical events in Songtrix are based on Midi events, but they represent more practical and convenient musical units.

For example, most musicians need to work with chords, whereas Midi has no concept of these and deals only with individual notes.  So Songtrix bridges the gap, allowing the musician to work with chord events which are translated into separate Midi notes for playback.

It also makes using Midi controllers much easier.  Where a pitch bend effect could take dozens of Midi events to achieve, the same thing can be done in Songtrix - even for a chord - with a single event.

For music production, Songtrix can capture the sound from your Midi Output device as a WAV or MP3 file, using the Export Song process.  Or it can export your song to a Midi file, where it can be used by audio production software for the final mix.