Apple's QuickTime software has the built-in ability to convert a MIDI file into a QuickTime Music file. These files can be played back on Macintosh and Windows computers with the QuickTime Musical Instruments Extension (included with QuickTime4). This extension is essentially a software-based General MIDI synthesizer. It works in tandem with the Macintosh QuickTime architecture to allow playback directly through the computer's audio output.
QuickTime Music
As with MIDI, QuickTime Music files are much smaller than their digital audio counterparts. And since it is a separate data type from QuickTime Audio and QuickTime Video, it can be combined with the others. For example you could have a QuickTime Movie with a digital audio narration track together with a QuickTime Music track playing in the background.

	Press the "play" button to hear a 30-second stereo "QuickTime music" music sample (10KB) using the QuickTime plug-in.
Otherwise, download a 2-minute "QuickTime Music" music example (10KB) for play using a helper app such as MoviePlayer. Note: If you have properly installed the QuickTime plug-in, clicking here will cause this file to play in a new window.
(QuickTime Music does not support audio per se, but voices and/or sound effects can be combined with a QuickTime Music track using a separate QuickTime audio track.)