I'd like to get comments on my current (green but hopefully budding) understanding of building a walking bass line in straight ahead jazz. What you have as you approach the notes to choose is suggested by the chord progression. Looking at an individual chord within the context of the rest of the progression will suggest a mode to select notes from. Or a subset of that mode will be the chordal notes themselves. The chordal notes, especially the 3rd and the 7th are best to define the current chord and should be used when wanting to state just what chord is occuring at the moment. Often, when trying to communicate the progression of the song, the bass should emphasize certain chords this way. Other options are using chord substitutes to add interest and sonic dynamics (hopefully that phrase communicates my thoughts) In doing the basics above, one must choose other notes from the suggested modes that lead well into the next chord, that compliment the melody and that create a melodic line that stands on its own. And of course, do this while staying in the pocket and providing rock solid rythym. Am I starting to get this??? Be brutally honest.