T, I have wondered about this, as well. As I pointed out, the interval and the harmonies, certainly were used, and in a fundamental enough way to make me skeptical that it would be hard to make much of a case that it was ever systematically avoided, in the way that, say, parallel fifths were--

Mbo, you know the secret, which is that it is actually a lot easier to do this stuff than to explain it!

Jon, I wish I could steer you to something that is easy to work with. Most theory stuff is not very easy to understand, and doesn't get straight to what you need, or what is useful. I think that goes double for stuff you find on the Web.

I recommend buying a copy of "The Harvard Brief Dictionary of Music", and just thumbing through it. The explainations are clear, brief, and, when you find something you don't undertstand, just turn to another page for the explanation of that.

I have said this a lot lately, in one way or another, but when you wade through an explanation (or a series of them) and finally understand the theory, it turns out to be simple. It is just the explanation that is so hard to understand.

Anyway, feel free to ask anything you want here..between the lot of us, someone will come up with an answer.