MIDI
Also known as: MIDI 2.0, .mid file, MIDI controller, DAW, MIDI CC, MPE
MIDI (Musical Instrument Digital Interface) is a protocol for transmitting musical performance data.
When you press a key on a MIDI keyboard, it sends a message saying 'note 60 (Middle C), velocity 90, on channel 1' -- not audio. The receiving device (synthesizer, software, drum machine) interprets this and generates the actual sound.
MIDI, explained at three levels
At home
MIDI is like sheet music for computers. When you play a MIDI keyboard, it doesn't record sound -- it records 'which key, how hard, how long'. Software or a synthesizer then plays those instructions as whatever instrument sound you want.
At work
Music producers use MIDI to compose and arrange music. Notes are recorded as data in a DAW (Digital Audio Workstation), then played back through software instruments. The tempo can be changed, notes edited, and instruments swapped -- because MIDI stores instructions, not audio.
At home
MIDI messages: Note On (pitch 0-127, velocity 0-127, channel 1-16), Note Off, Control Change (modulation, sustain pedal, volume), Program Change (instrument selection), Pitch Bend, and System messages (clock sync, SysEx device-specific data). 16 channels allow controlling 16 independent instruments simultaneously.
At work
MIDI over USB replaced the 5-pin DIN connector in modern equipment. DAWs (Ableton, Logic, Pro Tools, FL Studio) use MIDI for recording, editing, and playback via a piano-roll editor. MIDI clock synchronizes tempo between devices; MIDI Machine Control (MMC) controls transport functions (play, stop, record) across hardware and software. General MIDI (GM) defines a standard set of 128 instrument sounds for portable MIDI files.
At home
MIDI's 7-bit resolution (128 values) for velocity and control has been a long-standing limitation. MIDI 2.0 addresses this with 32-bit data resolution (4 billion values), per-note controller messages (allowing expression on individual held notes), and the MIDI Capability Inquiry (MICI) protocol for bidirectional device communication and configuration.
At work
MIDI is also used for stage automation and lighting (MIDI Show Control), audio software parameter automation (VST plugin control via MIDI CC), and generative music systems. MPE (MIDI Polyphonic Expression -- used in the Roli Seaboard) assigns each note to its own MIDI channel for per-note pitch bend and pressure, enabling expressive continuous control on polyphonic instruments.
Real-world examples
At home
Carlos connects a MIDI keyboard to his computer via USB. In GarageBand, he plays a chord and the software records it as MIDI data. He then changes the instrument from piano to strings -- the same notes play back with the new sound.
At work
Aisha uses Ableton Live for live performance. Her MIDI controller triggers samples and loops via MIDI messages, and MIDI clock sync keeps all devices (drum machine, synthesizer, effects) in time with the software's master tempo.
Common confusions
- MIDI files contain audio — MIDI files (.mid) contain only performance instructions -- notes, timing, velocity. They require a sound source (software synthesizer, hardware, or GM soundfont) to produce audio. A MIDI file on its own is silent.
- MIDI is only for keyboards — MIDI is used with keyboards, drum pads, wind controllers, guitars (via MIDI pickups), DAW automation, lighting systems, and software plugins. Anything that can send or receive note and control messages can use MIDI.
For analysts
MIDI is niche for most business analysts, but it appears in retail background music systems, event A/V setups, and media production workflows -- useful context when evaluating or specifying creative technology equipment.
History & origin
MIDI was developed collaboratively by Roland, Yamaha, Korg, and other synthesizer manufacturers and standardized in 1983. It was revolutionary -- previously, electronic instruments couldn't communicate. MIDI allowed one keyboard to control multiple synthesizers and enabled digital audio workstations (DAWs). MIDI 2.0 was released in 2020, adding higher resolution velocity, bidirectional communication, and per-note expression.