Tell Me About Music Composition

Even though my primary interest is animation, and I'm going to the online school Animation Mentor this coming January (which I'm really excited about), I am also deeply interested in music and making music. Ever since I was about 5 I've been playing the piano by ear (with a few brief piano lessons off and on, and I've still forgotten how to read music for the most part), and recently I've gotten a theremin and I've been getting fairly good at that. However, while I'm extremely good at recreating notes I hear, I'm not so great at real-time coordination and dexterity on the piano, and I'd like to get much better at both these instruments. I'm also very intrigued by "music theory", and I'd like to learn more about how to go about making music, and what makes music "flow" and sound good.

In short, I'd like to improve my musical side and learn to compose music. Are there any classes I could take if I haven't been regularly pursuing any kind of musical program throughout public school? Meanwhile learning animation in my new school?

Take an "Intro to Music Theory" class. Just about every school's got some theory classes, which are quite necessary if you're thinking about actually composing music. Just having rudimentary knowledge of basic music theory is more helpful than you'll ever know.