If you've been thinking about brushing up on your music theory, the World Wide Web is a great place to start. There are a number of sites offering quality music instruction for free. A prime example is Ricci Adam's MusicTheory.net, which presents a huge menu of music theory lessons and a cool selection of multimedia music training exercises at no cost.

Most of the lessons are pretty basic, but if you're a theory novice (or just looking for a bit of a refresher), this is a good place to start. Lessons cover such areas as key signatures, scales, chord theory, and basic composition.

Perhaps the site's most useful feature is its collection of exercises, or “Trainers.” At the time of this writing, there are ten different exercises available, broken up into three categories — Trainers, Ear Trainers, and Instrument Trainers. The first offers exercises dealing with notes, keys, intervals, and triads. The second consists of audio drills that help sharpen your skills in recognizing intervals, scales, and chords. The last provides practice on locating various notes on piano, guitar, and brass instruments.

The Trainers are well designed and make good use of audio. They can be downloaded, as well, if you'd rather use them offline. They're compatible with both Mac and Windows.

MusicTheory.net also offers a forum section, a chord calculator, and a Staff Paper Generator that lets you print your own blank music paper. While everything on the site is free, Adams provides links for giving a donation (using the Amazon Honor System and PayPal) if you're so inclined.