Most people I speak to about MIDI are confused about it on a fundamental level. So let’s start there. The MIDI sockets on your keyboard (for example) do not transmit sound of any kind, so you can’t record the voices from your keyboard to a computer via MIDI – only information about what is being played or pressed, switched or turned on the keyboard. MIDI is essentially a control language.
MIDI has values of 0 to 127 and 16 channels. For example, minimum volume is expressed as 0 and maximum volume is expressed as 127. No distortion is 0 and maximum distortion is 127. Pan far left is 0 and pan far right is 127. You see?
So, when you play a C key on your keyboard, the keyboard tells the computer program or DAW that you are playing a C. It tells it how hard you’re pressing, how long you’re holding it for, and when you let go. This information can then be recorded onto a MIDI track and/or used to trigger a sound in a virtual instrument. The confusion about MIDI sending sound seems to set in when people download a MIDI track from the internet, and when they play it, the sounds of the instruments play out of their speakers. The reality is, the MIDI track contains information that tells the computer what is being played, which channel it is assigned to, what instrument is on that channel, and so on. Your computer sound card runs with a piece of MIDI software that usually plays a set of instruments known as General MIDI instruments behind the scenes – there is no sound in the MIDI file, only information. General MIDI is a universal set of MIDI sounds shared by a lot of keyboards and sound modules. By universal, I mean that when you’re using General MIDI, instrument 01 is always acoustic grand piano, 59 is always tuba, and 115 is always steel drums, and French horn (my personal favourite) is number 61…and they always sound awful!
However, MIDI doesn’t stop with notes and chords; mixers, drums pads, even breath controllers can transmit MIDI information – you can even get devices to send MIDI from a guitar!
In my studio, I use MIDI quite a lot. I use MIDI to connect my electronic drum kit to my Superior Drummer and BFD virtual drum software. I use it to play in keyboard or piano parts from my USB MIDI keyboard, which triggers my Native Instruments virtual pianos, synths et cetera. My mixer sends MIDI via USB so that the faders on my mixer control the faders in my DAW software. I use MIDI pedals to change my guitar sounds in the studio and live. It’s used everywhere!