Knowledge, HUH! what is it good for?

Absolutely.... EVERYTHING.
okay, yelling caps are out of the way, onto what I mean. If you can't read music, you can't learn a bass line by reading it. If you don't know your scales, you're going to play bad notes. This cycles continues on through pretty much everything. Both of which are problems I have. I think I figured out another part of not being able to play what I hear in my head though. Tone. I hear notes played a certain way, or with distortion, reverb, whatever. The point is, I get frustrated when I can't play what I hear. I hear a mellow deep, slightly fuzzy guitar part, and I have to try and figure it out on a bright strat pushed through a clean guitar amp. That doesn't always work so nice. As far as basslines go, for me that's even harder. I do understand the basics of how to play, but I can never get the tone I want. Time too add to my wishlist....