This. Rhythm is *always* the most important thing. The three most important things in music are as follows: Rhythm Rhythm Rhythm With that out of the way... no, you do not *have* to learn to read music. Billy Sheehan doesn't know how to read music and last I checked he is a pretty accomplished musician. But just remember that if you're being compared to a guy who knows hows to read, knows theory, and has a great ear... he will win almost every time. Reading will help you. Sometimes you just want to play something... maybe it's a piano piece or something. So you Google and find the sheet music, and then you can play it. Easy. If you can't read, you might try searching for somebody else's TAB for hours, and probably they're all wrong anyway. So, go learn to read. But you'll also maybe be fine without it.