The development of inexpensive electronic musical instruments by 1980 prompted the need for a means of communication between them, and in 1981 a draft specification was put forward by Dave Smith of Sequential Circuits. This was adopted by the major manufacturers, and by 1985 the Musical Instrument Digital Interface or MIDI, as it became known, had become the standard means of interconnecting electronic musical instruments with each other and with computers.
It is important to realize that MIDI does not send or receive sound signals; it cannot be connected to an amplifier and loudspeakers to play music. The reason is that what MIDI primarily exchanges is note information. Every time a note is pressed or released on a MIDI instrument, a signal is sent from the instrument's MIDI OUT port to anything connected to it. In order to create sounds from these signals, some form of sound generation circuitry must be used. For example, pressing a note on a MIDI organ can send a signal to a synthesizer, and the corresponding note on the synthesizer will then sound. In this way, one instrument can be used to "play" another, or a "MIDI file" stored in a computer can be used to play an instrument. Other information such as pedal depressions, patch settings and the like can also be exchanged.
MIDI is a very simple interface, as such things go, and also very slow by today's standards; but it is cheap, reliable, ubiquitous, and perfectly adequate for all but the most demanding applications. For this reason it is tremendously popular, and any attempt to modify or replace it would meet strong resistance. It does allow for the use of "microtones" - that is, notes other than those in the twelve-note ET scale - but the implementation is rather inelegant and could prove too slow for complex music.
Those wanting to experiment with various tempering schemes can certainly use MIDI, but for experimenting with complex sound and waveform generation a new standard might be considered desirable. As the teK Project develops, this question is likely to arise increasingly often.