MIDI stands for musical instrument digital interface; it is a protocol that allows electronic musical instruments, computers and other devices to communicate with each other that was first introduced in 1983.

• MIDI messages can be used to transmit various types of musical information, including note data, controller data, program changes, and more; it does not transmit audio
• MIDI messages are sent over a standard 5-pin DIN cable, or more commonly these days, over USB
• It is a digital language that sends commands to electronic instruments to tell them to e.g. play notes, change instrument, add an effect etc…
• The list editor in Logic gives you an idea about the kind of commands you find in a MIDI file.
• MIDI allowed you to connect electronic instruments to a computer; the Atari ST (1985) had MIDI ports; it was successful because it was easy to program a sequence and send it via MIDI to control a synth or sampler
• MIDI controllers can be switched (on or off) or continuous (0-127); controller numbers 0-63 are reserved for continuous data, such as modulation and volume, and controllers 64-121 are reserved for switched controllers such as the sustain pedal
• A CV (control voltage) gate systems predate MIDI and are a way to connect and control different electronic musical instruments or devices in the late 60s, 1970s and early 1980s
• This is an analogue signal that is used to control parameters like pitch, volume, or modulation
• General MIDI (GM) is an updated MIDI specification that ensured more consistent sounds across devices
• MIDI 2.0 is a newer version of the protocol introduced in 2020, so it is still gathering ground with manufacturers
• Open Sound Control (OSC) is a language or protocol that enables you to network synthesisers, computers, and other multimedia devices. It is a modern standard that is sometimes used as an alternative to MIDI.

MIDI messages

• A byte consists of 8 bits; a MIDI message consists of a status byte and one or two data bytes
• A status byte tells us the type of MIDI message and the data bytes provide more information about the parameters associated with it – the MSB is the most significant bit and it is the furthest bit to the left
• The MIDI message is transmitted to different pieces of equipment using a specific order of bits and bytes.

• Velocity data is transmitted as part of the second data byte in a note on message
• Because binary is a base 2 system, the number of possible values is given by the calculation 2^x; 2⁸ = 256
• Status bytes always begin with 1 and data bytes always begin with 0 so we only really have 7 useful bits
• 2⁷ = 128 – there are therefore 128 possible values for a note’s velocity; 0 – 127
• Pitchbend messages use both data bytes to communicate a more accurate value
• Again, the first bit is always spoken for, so we have 2 sets of 7 bits to communicate the pitch bend value
• 2¹⁴ = 16384. 16384/2 gives pitch bend’s centre position as 8192.

The impact of MIDI

• MIDI revolutionised electronic music, allowing different types of electronic instruments to communicate with each other and with computers in a standard and universal way
• Musicians could record, edit, and manipulate the musical material in their performances, transposing, quantising and editing individual notes with ease
• The widespread adoption of MIDI contributed to the growth of electronic music genres like synthpop, techno, house and EDM
• MIDI also expanded the possibilities of live performance with electronic instruments; musicians could programme and trigger pre-prepared sequences
• Multiple electronic instruments could be played with one controller keyboard
• The development of MIDI paved the way for the creation of digital audio workstations (DAWs).