MIDI

MIDI
Name	Musical Instrument Digital Interface
Extension	.mid, .midi
Mime	audio/midi, audio/x-midi
Uniform type	com.apple.midi-audio

MIDI is a technical standard that describes a communications protocol, digital interface, and electrical connectors connecting a wide variety of electronic musical instruments, computers, and related audio devices. It allows devices from different manufacturers to communicate with each other, enabling the control of sound generation and the recording and playback of musical performances. The standard was first published in 1983 and has since become ubiquitous in the music industry, fundamentally changing the way music is produced, performed, and recorded.

Overview

The protocol transmits event messages that specify notation, pitch, velocity, vibrato, panning, and clock signals to set tempo, allowing devices to synchronize. This data can be recorded into a hardware or software device called a sequencer, which can then edit the data and play it back. Unlike digital audio files, these messages do not represent sound directly, but rather instructions on how to generate it, resulting in very compact file sizes. This system revolutionized music production by enabling complex arrangements to be created, edited, and controlled from a central point, such as a digital audio workstation like Ableton Live or Logic Pro.

Technical specification

The original specification uses a 5-pin DIN connector to carry an asynchronous serial connection with a 31.25 kbit/s data rate. Each message is composed of an 8-bit status byte followed by one or two data bytes. Key message types include Note-On and Note-Off commands, Control Change messages for parameters like modulation wheel and sustain pedal, and Program Change messages to select different instrument sounds. The standard also defines 16 logical channels, allowing a single cable to carry independent performance data for multiple instruments, a concept central to multitimbrality. System Exclusive messages allow manufacturers to transmit proprietary data for unique instrument parameters.

Development and history

The development began in the early 1980s through a collaboration between engineers from leading American and Japanese synthesizer companies. Key figures included Dave Smith of Sequential Circuits and Ikutaro Kakehashi of Roland Corporation, with early prototyping involving instruments like the Prophet-600 and Jupiter-6. The first public demonstration occurred in 1983, connecting a Sequential Circuits Prophet-600 to a Roland JP-6 at the National Association of Music Merchants show. This interoperability was a landmark achievement, leading to rapid adoption across the industry and the formation of the MIDI Manufacturers Association to oversee the standard.

Applications and impact

Its impact on music creation and performance has been profound, becoming the backbone of modern electronic music production, film scoring, and live performance. It enabled the rise of home studios by allowing inexpensive personal computers to control professional-grade sound modules. In live settings, it allows performers to trigger backing tracks, control lighting via DMX512, and synchronize complex stage shows. The standard also facilitated new forms of musical expression and composition, influencing genres from hip hop and dance music to contemporary orchestration in Hollywood, as used by composers like Hans Zimmer.

Hardware and software

Common hardware includes keyboard controllers, sound modules, drum machines like the Roland TR-808, and audio interfaces. Music workstations such as the Korg M1 and Yamaha DX7 integrated sequencing and sound generation. On the software side, sequencers and digital audio workstations like Steinberg Cubase, Apple GarageBand, and Avid Pro Tools rely on it for note entry and virtual instrument control. Virtual Studio Technology instruments and effects plugins within these hosts are almost entirely controlled via internal data streams, making it an invisible yet essential layer in modern production.

File formats

The Standard MIDI File (SMF) specification, developed by a consortium including Opcode Systems, allows sequences to be saved, exchanged, and played back on different systems. These files, typically with .mid or .midi extensions, contain header and track chunks that encapsulate the event data and timing information. The format supports multiple types, with Type 1 files containing multiple tracks synchronized to a single timeline, ideal for multi-part compositions, and Type 0 files merging all data to a single track. These files are widely used for karaoke backing tracks, mobile phone ringtones, and sharing musical notation on the internet.

Category:Audio codecs Category:Music technology Category:Computer file formats Category:Digital audio Category:1983 introductions