This post focuses on describing MIDI – what it is and what it does.
Musical Instrument Digital Interface (MIDI) was created in 1983 to address the need for controlling instruments electronically. As synthesizers grew more and more common, it became more and more difficult to control them all. MIDI was created to allow musicians to control many devices from one ‘controller’ keyboard. It was also created with a number of relatively robust features to aid in the creation of digital music.
MIDI does not transmit an audio signal or media — it simply transmits digital data “event messages” such as the pitch and intensity of musical notes to play, control signals for parameters such as volume, vibrato and panning, cues and clock signals to set the tempo. As an electronic protocol, it is notable for its success, both in its widespread adoption throughout the industry, and in remaining essentially unchanged in the face of technological developments since its introduction in 1983.
The most important thing to realize about MIDI is that it is not a sound signal. All MIDI consists of is a set of musical instructions that interpret musical input, such as from a keyboard, into a set of standardized instructions that another device can interpret back into sound. The sounds that result from MIDI are entirely created by the device that is being controlled and at no time does any audio get transfered over the MIDI cable.
The mapping of certain instruments to certain notes is called General MIDI. This allows compositions to be shared between devices while retaining the proper arrangement of instruments. Not all patches are General MIDI, in fact the majority of patches are simply a single instrument mapped across the entire 88 key range.
MIDI powered the music in the majority of video game consoles in the latter part of the 80s and into the 90s and was a popular format for trading music on the Internet (long before MP3s) due to its very small size. Of course, the compositions sounded different on every computer…
One particularly powerful feature of MIDI includes a rough implementation of timecode, allowing two or more devices to be synced together via MIDI messages.
MIDI cables have circular, five pin cables and generally have runs of less than 15 feet. Most professional soundcards come with their own MIDI interfaces, although they can be added on separately (typically via USB).
These days MIDI has been adapted to a large number of applications, from conversions of B3 organs into MIDI controllers to entirely virtual instruments, to controlling light shows.
One of the most successful technologies ever, MIDI turns 25 this year!