I'd want to get more understanding in music theory. I played sax and drums when I was a kid and have had lessons of notation, cycle of fifths etc. the "normal" stuff, but I'm not really able to use that in my bass playing. I'd really need to learn what notes to play over different chords. I can make up lines that sound intresting (at least to me) if I'm given enough time to explore, but I really suck in improvising anything on the fly. So basically I have to learn scales and modes, am I right? Where should I start? Would "The Chordal Approach" be a good book to start with?