MIDI - how pianos talk
It's all the notes and controls that a piano keyboard can send to a sound synthesizer over a wire.
Digital pianos have both a keyboard and a built in synthesizer. There are also "controller keyboards" that will use a software synthesizer on your computer.
Anything you can DO on the keyboard, midi can do too.
When you pick a sound, a teeny message goes across the midi cable.
When you press a key down, a teeny message goes across the midi cable.
When you release a key, well, you get the idea...
for notes, midi sends:
which one? Octave and note.
down or up? So really, there are 2 midi events per note. One down. One up.
how hard pressed/released? The "velocity" - a number from 1 to 127. 1=soft.
127=loud. 0 is used for note off.
which "channel" - a number that ties the note to a particular
sound and sound controls. Similar to a mixer channel but for notes.
for (sound) controls, midi sends:
which one? (HoldPedal, KeyboardPressure, ModWheel, ProgramChange, etc...)
set it to what? (usually a number from 0 to 127).
which "channel" - again, ties this sound control to the notes playing on
that channel.
Think of these little messages as notes being sent from a keyboard to a synthesizer.
They can also be stuffed into a midi file. These usually have a .MID or .KAR extension. Things sent over a wire happen in real time. In a midi file, these events are stamped with the exact time they happen at.
Midi cables let you seperate the keyboard controller from the sound module. Kind of like the way audio cables let you have seperate stereo components. So all your keyboards can go to one synthesizer or so one keyboard can go to lots of synthesizers. Also, computer programs can record and play back the exact same notes.
Computer programmers will enjoy Jeff Glatt's site
The official midi site is kinda meh midi.org
We're going to just chat about the useful stuff, though.