MIDI
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MIDI
What Is MIDI?
M.I.D.I (Musical Instrument Digital Interface) is a communicaion protocol for musical instruments. MIDI is a standard specification found in almost any electric synth, soundbank, or drum machines built after 1983.
In it's most basic form consists of data that describes a sonic envelope, duration, velocity, and a place holder within a tempo. This information can then be used with a variety of sounds, whether oscillators, samples etc.
This industry standard enables connections between a variety of devices from different manufacturers. MIDI put a powerful computer instrument networks and software in the hands of less technically versed musicians and amateurs and has provided new and time-saving tools musicians and programmers.
History
The System first appeared in 1982 following agreement among manufacturers of electronic musical instruments to include a common set of hardware connectors and digital codes in their instrument design. In 1983, the MIDI 1.0 sppecification was formally released by the International MIDI Association as Roland, Yamaha, Korg, Kawai, and Sequential cirtuits, all came out with MIDI-capable instruments that year. Midi has roughly remained unchanged since that date.
MIDI Time Code
MIDI Time Code (MTC is a sub-protocol within MIDI, and is used to keep 2 or more devices in Sync. Essentially, MTC follows the same format as SMPTE. (a non tempo based time code).
MIDI Clock
MIDI Clock is used to synchronize multiple MIDI devices. Unlike timecode which is based on absolute time values, MIDI Clock is based on the tempo of the song, and sends exactly 24 clocks per quarter note. You can use this formula to calculate the number of clocks sent per minute at a given tempo:
So, at a tempo of 80 beats per minute, it sends roughly 1920 clock signals per minute. To determine the clock frequency in milliseconds:
At 80 bpm, a clock signal is sent every 31.25 milliseconds.
MIDI Clock should only be used for synchronizing MIDI devices. It is not precise enough for audio and video.
