Arguably the Web's single most popular sound format, the MIDI file is everywhere these days. A small data file, a MIDI file contains a musical sequence that can drive your sound card or electronic musical instrument if it has General MIDI (GM), General Standard (GS) or Extended General MIDI (XG) compatibility. (Virtually all sounds cards do). If you've ever encountered a Web page that featured background music, odds are you're listening to a MIDI file. The same goes for if you've ever received a digital postcard. From classical music to rock 'n' roll to techno: no matter what your musical tastes, you can find your favorite tunes in MIDI format somewhere on the Web if you look hard enough.
A fine resource for free MIDI files, this site offers classic pop and rock tunes, as well as current Top 40 hits. There is also a good selection of MIDI tunes from cinema and TV here. The site includes a search engine, as well as a free newsletter.
This sound archive site, which has been around since 1999, serves up thousands of free sound files. Here, you'll find MIDI and WAV files from cinema and TV, as well as sound effects and files uploaded by users.
This site serves up thousands of MIDI sound files by over 1,800 classical composers. Most of the content here is free (but the number of files you can freely listen to per day is limited). A paid subscription (optional) gives you more features.
(Note: this site is occasionally inaccessible). If you're looking for the latest Top 40 pop hits in MIDI format, here's the place to go. Selections here range from rock to pop to hip hop and artists include everything from Ace of Base and Aqua to The Prodigy and Oasis.