I've got a great teacher and I take a lesson every two weeks. I'm going to ask him this question at my next lesson, but here it goes here first. It seems to me that I'm learning to do two things with my bass lines. First I am learning how to arrpegiate the different chord types. A major chord contains the notes found in the major scale, a minor chord contains the notes found in a minor scale, etc. The other thing I am trying to learn is how to figure out logical chord progressions when I don't have a chart to read from. The chord progression would be the structure of the song and the arrpegios would be the construction of the chords. Am I making sense so far??? I like to play along with recordings, so I need to figure out the key and chord progression by ear. I like blues and boogie woogie and a lot of those seem to be a l,lV,V or l,lV,ll,V progression. I suppose there are other chord progressions that are common to other types of music. Knowing which progression might be likely could help figure out the song by ear. Am I making sense?