Think of each channel as a separate musician in your electronic orchestra. The amount of electronic musicians that are used in a particular piece may vary anywhere from 1 to 16. A MIDI sequencer is a program that reads and sends the MIDI language. A MIDI sequencer can also save, load, and edit MIDI files in standard MIDI format. Notes can usually be entered via a computer keyboard or through a MIDI keyboard into a sequencer.
Most sequencers are computer programs, but some are built in to keyboards.
Without a sequencer to interpret MIDI, MIDI would be useless to us. M IDI works like any other language. The most common types of MIDI sentences describe musical notes. For every note in a piece, one sentence will specify the channel, what note to play, and how loudly to play the note. At the end of the note's duration, there will be another MIDI sentence to tell the note to stop playing.