MIDI, the Musical Instrument Digital Interface, is a standard that allows electronic musical instruments, computers, and related equipment to communicate. Rather than carrying audio, MIDI carries messages that describe musical events: which note was pressed, how hard, when it was released, which patch to select, and how controls such as pitch bend or the sustain pedal are being moved. A receiving device interprets those messages and produces the sound, so a single keyboard can drive many synthesizers and a computer can record and replay an entire performance as data.
The standard was developed jointly by competing synthesizer manufacturers at the start of the 1980s, led by figures including Dave Smith of Sequential Circuits and engineers at Roland, who saw that a common interface would let their products work together. The MIDI 1.0 Specification was published in 1983, and a working connection between instruments from different makers was demonstrated publicly at that time. Stewardship of the standard passed to the MIDI Manufacturers Association (MMA), which together with the Japanese AMEI maintains the specification.
The original MIDI 1.0 design defines both a physical layer and a data format. Physically it used a 5-pin DIN connector and an asynchronous serial link running at 31.25 kilobaud, with opto-isolated inputs to avoid ground loops between devices. The data format organizes information into messages on sixteen channels, divided into channel voice messages such as note on and note off, channel mode messages, and system messages including system exclusive (SysEx) messages that let manufacturers send device-specific data. The detailed specification published by the MIDI Association sets out these message layouts and the serial transport, and notes that enhancements were added to MIDI 1.0 between 1983 and the consolidated 1996 revision.
Because MIDI describes events rather than sound, it is compact and easy to edit. A few kilobytes can represent a long, multi-instrument piece, and a sequencer can change tempo, transpose, or reassign instruments after the fact without re-recording. This made MIDI central to computer music, where it linked software sequencers to hardware sound modules, and it became a fixture of the General MIDI sound-set convention that standardized instrument numbering so files would play back recognizably on different equipment.
MIDI 1.0 proved unusually durable, remaining compatible across four decades of music hardware and software. Its message model influenced how digital audio workstations represent performances, and it was eventually extended by MIDI 2.0, which adds higher-resolution controllers and bidirectional negotiation while preserving backward compatibility with the original 1983 standard.