MIDI (Musical Instrument Digital Interface)

MIDI (Musical Instrument Digital Interface) is a technical standard that describes a communications protocol, digital interface, and electrical connectors that connect a wide variety of electronic musical instruments, computers, and related audio devices for playing, editing and recording music. A single MIDI link through a MIDI cable can carry up to sixteen channels of information, each of which can be routed to a separate device or instrument. This could be sixteen different digital instruments, for example.

MIDI carries event messages, data that specify the instructions for music, including a note’s notation, pitch, velocity (which is heard typically as loudness or softness of volume), vibrato, panning to the right or left of stereo, and clock signals (which set tempo). When a musician plays a MIDI instrument, all of the key presses, button presses, knob turns and slider changes are converted into MIDI data. One common MIDI application is to play a MIDI keyboard or other controller and use it to trigger a digital sound module (which contains synthesized musical sounds) to generate sounds, which the audience hears produced by a keyboard amplifier. MIDI data can be transferred via MIDI cable, or recorded to a sequencer to be edited or played back.

A file format that stores and exchanges the data is also defined. Advantages of MIDI include small file size, ease of modification and manipulation and a wide choice of electronic instruments and synthesizer or digitally-sampled sounds. A MIDI recording of a performance on a keyboard could sound like a piano or other keyboard instrument; however, since MIDI records the messages and information about their notes and not the specific sounds, this recording could be changed to many other sounds, ranging from synthesized or sampled guitar or flute to full orchestra. A MIDI recording is not an audio signal, as with a sound recording made with a microphone.

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