Unit
- Instructions, not audio: MIDI (Musical Instrument Digital Interface) carries no sound whatsoever. It transmits performance instructions such as which note to play, how hard to play it, and when to release it, leaving the actual sound generation to a synthesizer, sample library, or hardware module receiving the data.
- Historical origin: The protocol emerged in 1983 as a joint effort among synthesizer manufacturers who needed a common language so keyboards from different companies could trigger each other. This standardization prevented a fragmented market where every brand required proprietary cables and formats.
- Message-based architecture: Every action a performer takes, pressing a key, bending a pitch wheel, adjusting a mod wheel, generates a discrete digital message. These messages are small, structured, and transmitted in real time or stored for later playback inside a sequencer file.
- Serial data stream: Classic MIDI hardware transmits data serially at a fixed rate of 31,250 bits per second, a design choice from the early 1980s that still defines the timing resolution constraints programmers must work within, even in modern USB-MIDI contexts.
- Separation of composition and timbre: Because MIDI stores note events rather than waveforms, a single MIDI file can be replayed through a grand piano sample library, a synthesizer patch, or an orchestral string ensemble, producing radically different sonic results from identical performance data.
- Editability advantage: Since MIDI data is symbolic rather than acoustic, individual notes can be transposed, lengthened, deleted, or have their velocity changed after recording without any audio degradation, a flexibility that recorded audio waveforms cannot offer.
- Channels and polyphony: A single MIDI cable or virtual port can carry data for 16 independent channels simultaneously, each addressable to a different instrument or sound, enabling complex multi-instrument arrangements to travel through one connection.
- Universal adoption: Beyond music production, MIDI now controls lighting rigs, stage effects, karaoke machines, and even some art installations, proving the protocol's original design was flexible enough to outlast its initial keyboard-to-keyboard purpose by decades.
Design Principle
Principle: Separation of Structure and Timbre
Definition: A core principle in digital music systems where the instructional data (notes, timing, dynamics) remains independent from the sound-generating engine that interprets it.
Application: A composer scoring a film scene can write an entire cue using a placeholder piano sound, then swap the output to a full orchestral template without re-entering a single note, because the underlying MIDI data never changes, only its sonic interpretation does.
Quick Revision
- MIDI transmits performance instructions, not audio waveforms.
- The protocol was standardized in 1983 to unify instrument communication across manufacturers.
- Data travels as discrete messages over a serial connection at 31,250 bits per second.
- One MIDI file can produce different sonic results depending on the instrument receiving it.
- Sixteen channels can be addressed simultaneously through a single MIDI connection.