MIDI can be used in many ways. You can use it to take remote control of a bit of kit or to record what a bit of kit is doing to a sequencer.

Also you have midi instructions, these are things like Start or Stop or change to this patch number. Or you can set these instructions to transmit at a specific time or after a specific event.

Or you can record input into a midi device like a keyboard or a guitar (as long as it has a midi pickup). In this instance information about note pitch and duration and how loud the note is (rather than audio as we know and love it) is sent to and recorded buy a sequencer. This information is not audio is is just like a set of instructions which needs to be turned into audio via a midi sound module (a synthesizer) which will assign a voice to the instructions stored in the sequencer. Consequently you can swap between guitar, piano and horn sounds.

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