Monday, January 28, 2013

MIDI (Musical Instrument Digital Interface)

MIDI is short for "Musical Instrument Digital Interface", Perhaps the best way to understand the meaning of MIDI is to first understand what it is not:
  • MIDI isn't music
  • MIDI doesn't contain any actual sounds
  • MIDI isn't a digital music file format like MP3 or WAV
MIDI is nothing more than data -- a set of instructions. MIDI data contains a list of events or messages that tell an electronic device (musical instrument, computer sound card, cell phone, et cetera) how to generate a certain sound. Here are a few examples of typical MIDI messages:
  • Note On signals that a key has been pressed or a note on another instrument (like a MIDI guitar or clarinet) has been played. The Note On message includes instructions for what key was pressed and at what velocity (how hard the note was played).
  • Note Off signals that the key has been released or the note is done playing.
  • Polyphonic Key Pressure is a measurement of how hard a key is pressed once it "bottoms out." On some keyboards, this adds vibrato or other effects to the note.
  • Control Change indicates that a controller -- perhaps a foot pedal or a fader knob -- has been pressed or turned. The control change message includes the number assigned to the controller and the value of the change (0-127).
  • Pitch Wheel Change signals that the pitch of the note has been bent with the keyboard's pitch wheel.

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