The sound generator for this site and all its musical examples is the midi format. Since midi files are typically small and can be imbedded within Netscape generated web pages using Apple's QuickTime software, this combination of software creates the ideal situation for teaching music theory over the web. The trade off is that midi instruments and performances are typically lacking in sonic grace. However, as this technology becomes more important on the web, things should improve. I have given you one suggestion below on how to improve the sound quality of the midi files.
Apple's QuickTime software allows your computer to play back midi files either through its internal speaker or through external midi devices. Once you have Netscape and QuickTime installed, the playback of midi files is transparent. That is, you don't need to do anything other than clicking a playback button on the web page. You don't have to configure any helper apps, open new windows, or any number of other intermediary steps.
The version of the QuickTime software you will need is 2.5. The software is available for free at Apple's QuickTime homepage, and you can go to the QT homepage by clicking the QuickTime logo at the top of the page. As well as the basic software, make sure you get the QuickTime Plug-in 1.1 for Netscape. Also get the MoviePlayer 2.1.3, and the developers tools. While these latter items are not necessary to use this web site, I thought I could teach you how to make your own QuickTime sound tracks. Once again, follow the installation instructions. If you have any trouble, call me and I will help you. Once you have the software installed, open the control panel called QuickTime Settings. Select Music from the pop-up menu, then click QuickTime synthesizer. Your machine should be ready for midi playback.
You can improve the sound quality of midi files, by redirecting the output to more sophisticated midi devices. In the QuickTime Settings control panel, you can redirect the output by selecting other options, such as OMS (Open Music System by Opcode). To use any of these other options, you must have the proper software and device. For example, to use OMS, you must have OMS 2.3.1 installed, you must have an external midi device, such as a midi box or midi keyboard (that is not just a driver). Fortunately, you can obtain OMS for free from Opcode's download site. Make sure you get OMS 2.3.1 Install.hqx for Mac computers. There is also a Windows version. The only thing that is not free is the external midi device. Unfortunately, I cannot help you with that problem.
If you take the time to set-up your computer properly, not only will you get the most out of this site, but you will inspire me to make this site be the best that it can be. Thank you.