Watch the So Now What? online guitar lesson by Andrew Ford from Essentials: Walking Bass Lines

For the first 16 bars we will be playing Dm7, the Dorian scale is the scale of choice over this chord though we make liberal use of chromatic passing tones. In the second half of the B section we will think Db major scale instead of the Eb Dorian scale in our walking process, as Paul did on the original track. Db major scale shares the same notes as Eb dorian. We start the bass line with 8th notes, propelling the song forward with the two D's and continue to climb up diatonically with E, the 2, and F, the minor 3rd, we end the bar with the 6, part of the Dorian scale. The next bar starts on the 5th, A, but again we are thinking in longer phrases here and not bar to bar. From the A we walk down to the minor 3rd, F, the 2, E, and down to the 5 and octave lower. Bar 3 starts on the root, D, and goes down to F, the minor third, low E, the 2, and ends the bar on a chromatic Ab that leads us to the A, our 5, in bar 4 and here is where we play our minor 6, Bb, part of the natural minor scale, we finish this 4 bar phrase with C, the b7, and Db which leads us to the D or root in bar 5. Bar 5 begins like bar 1 with skipping 8th notes but 1-5 this time instead of two roots. We follow that with another diatonic walk up, E, F, and G, continuing that walk to the next bar with the 5, A. Bar 6 continues with the 2, E in a 1-4 movement then down to C, the b7 and lastly to Db which is again used as a transitioning note. The next bar begins with D, the root, going down to F, the minor 3rd, followed by G, the 4, walking up chromatically using Ab to A the first note of bar 8. Bar 8 follows A with C, the b7, E, the 2, chromatically down using Eb to the root D in bar 9. This bar has another chromatic walk down, D, Db on beat 2, C, b7, and skipping to Bb, the minor 6 that transitions to A, the 5 and 1st note of our new bar. We jump up from A to F, the minor 3rd, down to the 2, and back up to the 5, A. We start exploring new areas of the fretboard in bar 11 starting with D at the 7th fret of the G string. We walk up diatonically to the 2, E, the minor 3rd, F as an 8th note and the second 8th note being a ghost or muted note on the D string leading to Bb, the minor 6 and connects us to A, the 5, in bar 12, we continue to walk down in that bar from A to G, the 4, F, minor 3rd, E, the 2, and into the new bar, 13, with the root D. Bar 13 begins a skipping figure using wide intervals and open strings for effect. Starts on open D and moves to F at the 10th fret of the G string, back to D and then back to F before ending with another Bb leading us to A in bar 14. We have a pattern walk in bar 14 where we are walking down in thirds, first major and then minor third intervals, A to F then G to E. In bar 15 we have a common box shaped pattern that can be used over minor and dominant chords because there is no third, we have, D, root, then the octave, D, b7, C and the 5, A. From the A we walk down to the 4, G, the minor 3rd, F, 2, E, and to the root, D in bar 16.

Now bar 17 is where we change to chord number 2 of our two chord song. We go up a half step to Eb minor 7. Here I think Db major scale for half of the 8 bars of Ebm7, If you play the Eb dorian scale starting on Db, you get the Db major scale. Ok, the first 4 bars highlight the Eb dorian scale, we start on the root, Eb, then Db, the b7, C, the 6 and Gb, the minor 3rd, in the second bar,18, we play as an extension of bar 17 with the first note being F, the 2, then down to the b7, Db, to Bb the 5, and lastly a chromatic note D that leads us up a half step to Eb, the root in bar 19, to the 5, Bb, walk down chromatically to A, then Ab the 4 which gets us to Gb in bar 20, down to Eb, the root, A, a chromatic note leading to the 5, Bb. Now in the next four bars we are still playing Ebm7 but we outline the Db major scale. We start on the root Db, to the 4, Gb, the 2, Eb, then the 5, Ab. These translate to the b7, minor 3rd, root and 4 of Eb dorian. Back in Db for the 2nd bar we start on the major 3rd, F, Ab, the 5, major 7, C, and the 6, Bb. For bar 23 we have the root, Db, major 7, C, Ab, the 5, and Bb, the 6. The last bar of this phrase starts on the 4, Gb, the 5, Ab, major 3rd, F, and the root, Db.

Next we are back to Dm7 for the last 8 bars. We begin with a triplet to help define the new section. Notes are D, F, and G, root, minor 3rd, and 4. Second beat is the b7, C, the 6, B, then Bb that connects us to the A in bar 26 which is the 5, down to G, the 4, to F, the minor 3rd, and back to the 5, A. Bar 27 walks diatonically up the D dorian scale from D to E, F, 1,2,3 then skips to the 5, A. The last bar of this phrase starts on F at the 10 fret of the G string which is the minor 3rd, down to the 2, E, to C, the b7 and finishing on A, the 5. Our last 4 bars of the song start on the root D, to the b7, C, skipping 8th notes on beat 3 which are Bb, the minor 6, to G, the 4, moves up to A in bar 30, then walks back down diatonically to G, F, and E, 4, flat 3, and 2. Another swinging skipping phase on beat 1 with 8th notes playing 1 and 5, D and A, this walks up to a chromatic note, C# that leads to D, the root back down to another chromatic note Ab, and finally to A, the 5, F, the minor 3rd, E, the 2, and a chromatic connector Eb that gets back to the top.