When I was a young player, I was hungry to play jazz, and in particular walking bass lines. It took me a long time to find someone who was able to explain to me, from a technical standpoint, how you created the sound of “jazz licks,” and how you improvised and walked over chord changes. In fact, it wasn’t until I took a lesson with Jeff Berlin when I was sixteen that my eyes started to open. He was the first on that was able to explain to me what a walking bass line was.
If you’re reading this and you’re interested, this is how you build a walking bass line: chord tone (usually the root of the chord,) scale tone, chord tone, passing tone. That’s a very cut and dry explanation, but those are the basics. For example, if you’re playing 4 beats to a measure, and the chord you’re walking over is C, the notes in the chord C are: C – E – G. We’ll also assume that the chord C, in this case, is in the key of C, meaning you’ll use the notes from the C major scale for the scale tones (C-D-E-F-G-A-B-C.) So, a walking bass line over this chord might be: C (chord tone and root of the chord,) D (scale tone,) E (chord tone,) and then the last note will be a passing tone (a note a half step above or a half step below the root of the next chord in the song. (So if the next chord is F, you’ll play F# or E.)
To re-iterate, if we’re reading a chord chart that asks us to walk over a C major chord for four beats, and then moves to an F chord for four bars and then back again, we might play: C D E F# | F G A B. This is the simple explanation, and we are not tied rigidly to these rules. Ultimately, a good walking bass line should create an interesting counter melody that provides a strong harmonic foundation for the other players to play against, and the technical “rules” can be quickly cast aside, as long as what we’re playing outlines the chords in a clear and musical way.