Walking bass lines

Nothing has helped me improvise as much as learning to write (and improvise) walking bass lines. When you think about it, these lines have everything you need:

*They outline the chord tones of the chords in any particular set of chord changes. 

*They are melodic. They can go up and down the scale, hitting the chord tones, or can be arpeggiated.  So they are scales + arpeggios. 

*They have chromatic (non-scale) tones as leading tones to the scale tones. They can have "enclosures" (a word I learned today!), in other words, approaches to the target notes from chromatic leading tones above and below in the same phrase.  

If you can improvise a bass line on a set of chord changes, you can improvise a melodic line as well, because you are already doing it. The differences:

*The walking bass line is almost all quarter notes. The improvised melodic line will be mostly eighth notes and triplets, with a much more irregular rhythm, and including pauses between phrases. 

*The bass line tends to hit the chord root on the first beat of the measure, or beat 3 if the chord changes there. You can begin a chord on a note other than the root, but while learning I tend to just use the root every time. The treble melodic line emphasizes all the other chord tones except for the root. 

I'm developing the technique of playing a bass line and then improvising above it with a melodic line. It isn't easy for me. The treble lines come out very stiff sounding, stiffer than if I am simply playing block chords in the left hand. My ideas sound more limited than when I have other kinds of accompaniments.   

I learned bass lines for the first section of "Autumn Leaves" in all twelve keys this summer. This meant learning 2-5-1 progressions in both major and minor in every key, cycling downward through the circle of fifths. I have also improvised many hours over "Bemsha Swing," but just in one key. I can't get a good bass line for this song, since the movement of the chords is already so chromatic it doesn't seem to leave much space.  I guess I'll have to look at one from a record to see some of the possibilities here.