MIDI musical instrument digital interface Pronounced "middy," this connectivity standard enables you to hook together computers, musical instruments, and synthesizers to make and orchestrate digital sound. The term is used to describe the standard itself, the hardware that supports the standard, and files that store information that the hardware can use. MIDI files are like digital sheet music--they contain instructions for musical notes, tempo, and instrumentation--and are widely used in game soundtracks and recording studios. See also: sound