The MIDI standard that’s used to control loads of guitar equipment seems really complicated. Most devices will give you a painless way of programming your amp or equipment to avoid having to learn any of the codes, but occasionally there will be a device or occasion that requires a slightly more in depth look. The good news is that as a guitarist/ guitarists tech you can ignore nearly all of MIDI apart from program change and controller change.
The MIDI cable
It’s usually a 5 pin DIN cable, though others are possible. The midi cable has a send wire, a receive wire, and a ground. The other pins in a 5 pin are not connected. You shouldn’t need to know the pinout or which pin is which.
What is a MIDI communication?
Basically when you do something on a midi device, it sends 4 or three binary numbers down the send line. In a 4 number version, this is what the numbers are saying:
- <this is what I’m gonna tell you (code 0-15)>
- <but only devices on this special channel should listen to me (0-15)>
- <some more detail about what I’m gonna tell you (0-127)>
- <this is the data, usually a number between 0-127>
- <control change (9)>
- <channel 4>
- <volume control (7)>
This all gets picked up by the receiving device(s) on channel 4 which act(s) accordingly. In this case, it will change the volume to 56 (out of a maximum 127).
Technically, I’ve oversimplified, as the first two 0-16 numbers are rather confusingly sent as one combined binary number (common practice in serial comms), but that’s the gist of it.
This explanation was written in response to a facebook query. Hope it helps some others too.