Web Design in a Nutshell, 3rd Edition

MIDI (.mid)

MIDI (which stands for Musical Instrument Digital Interface) is a different breed of audio file format. It was originally developed in the early 1980s as a standard way for electronic musical instruments to communicate with each other.

A MIDI file contains no actual audio information (the digital representation of analog sound), but rather numeric commands that trigger a series of notes (with instructions on each note’s length and volume). These notes are played by a MIDI player using the available “instrument” sounds in the computer. The function is similar to the way a player piano roll creates a song when run through on the player piano.

As a result, MIDI files are incredibly compact and ideal for low-bandwidth delivery. They are capable of packing a minute of music into just 10K, which is 1,000 times smaller than a one-minute uncompressed WAV file (approximately 10 MB).

QuickTime and most other MIDI file handlers install a General MIDI (GM) soundset with instruments like piano, drums, bass, orchestral strings, and even vocal “oohs” and “aahs” in standardized MIDI locations. Although these sounds may vary in quality and timbre from player to player, General MIDI files can depend on getting a piano sound when they send to Program 1, Channel 1 of the GM Player (built into QuickTime, etc.). These sound sets can be surprisingly good, but they still can’t compete with recordings created in a studio. In general, MIDI files will always sound “computery.”

Despite this limitation, ...