MIDI stands for Musical Instrument Digital Interface. It is a standard, first published in 1983 by the International MIDI Association (IMA), that allows different musical instruments (commonly keyboards, but also guitars, violins, etc.) and devices (synthesizer modules, computers, sound cards, etc.) to communicate with each other.
(You've got the questions, haven't you now?) Well, if you're using a Mac, be sure you have the latest version of QuickTime (2.5 as of this writing) and the QuickTime Musical instruments in your System Folder.
If you are using a PC, I don't know what you need. Sorry, I'm PC illiterate. But I think you need a Sound Blaster card(?)
Mac or Windows: Download the latest version of the MIDPlug from Yamaha (http://www.yamaha.co.jp/english/xg/html/mplug.html)(long, huh?). It's a "soft synthesiser", which means that it has the musical instruments you need in software, it's available for Macs and Windows, and for Netscape and IE, so now you can hear the music!
Of course, that's not the only plug-in available. There's also the ever popular Crescendo and a few others I can't remember right now (it's the end of the day...), but I'll get them in here soonly. For now, try the Yamaha one. I highly recommend it (and they don't even pay me).
Do that, then come back hear and click on the "Yes" button to enjoy the music!
Questions? Corrections? Love Letters? email me!
MIDI data consists of signals, in the form of a series of codes or "events" that tell an instrument or synthesizer, "start playing this note at this volume," "stop playing this note," "play this channel using this instrument sound," and so on. Of course it is actually more complex than this, but essentially the important notion to grasp is that MIDI data does not describe the sound of the instruments used in a song (in most cases, anyways), but rather how those instruments are used (i.e. played) to form the entire song.
In the case of this site, MIDI is used to provide background music while you choose an image to view. There is a file embedded in here that sends data to your operating system asking (telling) it to play these notes, with these instruments, at this tempo etc. If your computer is able to provide the sounds needed, and your browser is able to interpret the data for your system, you will here music!
What do I need to hear the music?