MIDI (Musical Instrument Digital Interface, IPAEng: ˈmɪdi) is an industry-standard protocol defined in 1982 that enables electronic musical instruments such as keyboard controllers, computers, and other electronic equipment to communicate, control, and synchronize with each other. MIDI allows computers, synthesizers, MIDI controllers, sound cards, samplers and drum machines to control one another, and to exchange system data (acting as a raw data encapsulation method for sysex commands). MIDI does not transmit an audio signal or media — it transmits "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 widespread adoption throughout the industry.

All MIDI compatible controllers, musical instruments, and MIDI-compatible software follow the same MIDI 1.0 specification, and thus interpret any given MIDI message the same way, and so can communicate with and understand each other. MIDI composition and arrangement takes advantage of MIDI 1.0 and General MIDI (GM) technology to allow musical data files to be shared among many different files due to some incompatibility with various electronic instruments by using a standard, portable set of commands and parameters. Because the music is simply data rather than recorded audio waveforms, the data size of the files is quite small by comparison.

History

By the end of the 1970s, electronic musical devices were becoming increasingly common and affordable. However, devices from different manufacturers were generally not compatible with each other and could not be interconnected. Different interfacing models included analog control voltages at various standards (such as 1 volt per octave, or the logarithmic "hertz per volt"); analog clock, trigger and "gate" signals (both positive "V-trig" and negative "S-trig" varieties, between −15V to +15V); and proprietary digital interfaces such as Roland Corporation's DCB (digital control bus), the Oberheim system, and Yamaha's "keycode" system. In 1981, audio engineer and synthesizer designer Dave Smith of Sequential Circuits, Inc. proposed a digital standard for musical instruments in a paper for the Audio Engineering Society. The MIDI Specification 1.0 was published in August 1983.

Since then, MIDI technology has been standardized and is maintained by the MIDI Manufacturers Association (MMA). All official MIDI standards are jointly developed and published by the MMA in Los Angeles, California, USA (http://www.midi.org), and for Japan, the MIDI Committee of the Association of Musical Electronic Industry (AMEI) in Tokyo (http://www.amei.or.jp). The primary reference for MIDI is The Complete MIDI 1.0 Detailed Specification, document version 96.1, available only from MMA in English, or from AMEI in Japanese.