[[Category:Music and sound]][[Category:Electronic Component]]
''Musical Instrument Digital Interface (MIDI)''
The original MIDI (Musical Instrument Digital Interface) protocol was developed in 1983 by Dave Smith and Ikutaro Kakehashi to enable communication between electronic instruments.
== Software Protocol ==
Basically transmits commands like key onUnlike audio protocols that transmit sound waves, key offMIDI carries event messages—instructions about what to play, plus pitch/volume parametershow to play it, and when.These messages include:
Write more*Note On/Off: Triggers a note (e.g., "play middle C") and stops it.*Velocity: Indicates how hard a note is struck (volume or intensity, typically 0-127).*Pitch Bend: Adjusts a note’s pitch in real-time.*Control Change (CC): Modifies parameters like volume, pan, or modulation (e.g., CC#7 for volume).*Program Change: Switches instrument sounds (e.g., from piano to violin). MIDI doesn’t contain audio data; it’s a set of commands that a synthesizer, sampler, or software interprets to generate sound. This makes MIDI files tiny compared to audio files—think kilobytes versus megabytes. A MIDI message is typically 1-3 bytes long: *Status Byte: Defines the message type (e.g., Note On) and channel (1-16).*Data Bytes: Provide specifics (e.g., note number, velocity). The 16-channel system lets one controller command multiple devices or voices independently. For example, Channel 1 could trigger a drum kit while Channel 2 plays a bassline.
== Hardware Protocol ==
* MIDI is one-directional (MIDI OUT implements only TX, no RX, and MIDI IN implements only RX, no TX)
* There are no control signals like CTS/RTS/DSR/DTR used
The standard in MIDI interface was the MPU-401, first introduced as a standalone hardware by Roland in 1984, and then integrated into PC soundcards.
The MPU-401 had 2 modes:
* In UART mode, it acted as any other MIDI interface, passing MIDI data between the computer and external MIDI devices
* In intelligent mode, the PC offloaded the MIDI playback task to the interface, freeing the PC to do other tasks while the music was playing
== Schematic ==
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== General MIDI ==
General MIDI (GM) is a standardized specification for electronic musical instruments and synthesizers, introduced in 1991 by the MIDI Manufacturers Association and the Japan MIDI Standards Committee.
General MIDI aimed to ensure consistency across devices by defining a uniform set of 128 instrument sounds (called "patches"), such as piano, violin, and drums, organized in a specific program change order, along with standardized channel assignments (e.g., channel 10 for percussion).
This allowed musicians and composers to create music that would sound reasonably similar on any GM-compliant device, solving the patchwork compatibility issues of early MIDI systems.
General MIDI largely superseded the previous Roland MT-32 de-facto standard and quickly became foundational in music production, video game soundtracks, and consumer electronics.
== Weblinks ==
* http://en.wikipedia.org/wiki/Musical_Instrument_Digital_Interface - wikipedia on MIDI in general
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