This document gives a general introduction to the world of computer-delivered sound. It is assumed that you will be using some sort of sound editing software which gives you some choices. See Music Software for a list of free or shareware software for editing or converting sound and MIDI files.
CD: This format is only available on music CDs, and not as a computer file format. Before you can do anything with this format, it must be converted. DVDs also deliver sound content, but since it supports 5-channel surround sound, it should be avoided for sound-only tasks.WAV (.wav): This native Windows file type is the largest of the computer sound formats. Choosing lower bit rate and stereo vs. mono can reduce WAV file size, but even WAV files at the lowest quality and smallest bit rate are much larger than same-length MP3 files at CD quality. Small WAV files (such as sound effects) are appropriate for download, but avoid offering anything of length in this format on-line.
MP3 (.mp3): MP3 files are like JPEG image files – they require some processing when opened. Older Windows95 machines may not have a compatible player, but Windows Media Player on W95b or above will handle them, and you can always offer a link to any of a dozen MP3 players (see Software) to be safe. MP3 files come in a range of compression levels, and can rival CD quality at about 1/10th the file size of a WAV or CD – that’s what all the fuss is about!
RealAudio (.ra), QuickTime (.qt), Windows Media (.wma): These file types are proprietary, and so are not universally supported by editors. WMA can be played by almost any player, but RA and QT require their respective players (free, but must be downloaded and installed). To edit any of these three formats, you'll have to buy something. There are also other formats emerging.
MIDI (.mid): MIDI files beat all the others hands-down for size - most are 10k or less! (Yep, that's kilobytes!) This is accomplished because a MIDI file contains no actual sounds, since the sounds are actually provided by the MIDI playback device on the client computer (usually the sound card). The quality of playback on most generic sound cards is pretty poor. However, MIDI files are so small that you can safely allow students to download, play with, and post on their websites, to their heart’s content!