Below are a list of common formats for audio.

Format	MB Per Sec	Description
WAV	11 MB (Uncompressed)	Windows format for wave files, can be compressed using various codecs to save space.
MP3	1 MB	The new audio sensation by the Fraunhofer Institute. Allows a CD Quality track to be crammed into a 4mb file.
MID	< 1 KB	MIDI files tell the computer what notes/instruments to play, and does not contain any audio information, hence it's small size.
AU	??	Cross platform format for Windows and Apple computers.