MIDI is the language of electronic instruments, it’s how they talk to each other. They use it to exchange musical information regarding notes, timing, and configuration. The electronic instruments can be synthesizers, sequencers, drum machines, but also DJ equipment, guitar effect pedals, looper pedals, or even computers running diverse software (in particular DAWs).
MIDI is a digital protocol, just like USB or WiFi, it only sends 0’s and 1’s. And it does not involve any audio, only information and commands, which we call “messages“.
For example:
- Your synthesizer can play a sound if you press a key on it – the same can happen if it receives a MIDI Note On message
- Your stage piano can change its instrument sound to Xylophone if you reconfigure it – the same can happen if it receives a MIDI Program Change message
- Your drum machine can start the beat if you press its play button – the same can happen if it receives a MIDI Start message
Here are the most common MIDI Messages:
- Note On/Off: These 2 messages respectively start and stop playing a note. They indicate which note is being played and how hard it is struck.
- Control Change (CC): This message changes the value of a specific “controller”, e.g. volume, modulation, or pan.
- Program Change (PC): This message changes the instrument sound or patch on a synthesizer or other sound module.
- Aftertouch: This message indicates pressure applied to a key after it has been struck.
- Pitch Bend: This message adjusts the pitch of notes in real-time.
- System Real-Time: These messages are used to control tempo and start/stop a sequence. Read here for more info about Real-time messages.
- System Exclusive (SysEx): These are “wildcard” messages, used for any command or that does not fit the other message types.
A series of MIDI messages can be stored on a computer in a *.mid file for example. Then it is possible for a software to “play” the file, which may sound like a song if the file is full of “MIDI Note On” and “MIDI Note Off” messages.
Similarly, the same series of messages can be transmitted over a MIDI Cable connecting two devices.
Overall, MIDI is a powerful tool for composing, recording, and performing music, offering a level of control and flexibility that’s been crucial in the development of modern music technology. It has been around since the 1970’s and it’s still extremely used to this day.
