Here is an example of how chord substitutions can be tied to a bass line. The first chord progression is in Bb below. Think of the progression as a waltz where each chord is played for two measures. (///) (///)
Bb (///) (///)
Am7b5 (///) (///)
Gm7 (///) (///)
F7 (///) (///)
Ebmaj7 (///) (///)
Dm7 (///) (///)
Cm7 (///) F7 (///)
Bb (///) D7 (///)
Now, recognize that the progression is simply a descending chromatic line starting on 1 or 8 and then going down 8-7-6-5-4-3-2/5-1.
Here is another set of chords you could use to accomplish the same thing:
Bb (///) (///)
Cm6 (///) Am7b5 (///)
Gm7 (///) Gm7/D (///)
F7 (///) F13 (///)
Ebmaj7 (///) Ab9 (///)
Dm7 (///) Dbm7 (///)
Cm7 (///) B7#9 (///)
Bb (///) F#m7b5/A (///)
In the second line, Am7b5 and Cm6 sub for each other. Play them both!
In the fifth line, playing Ab9 after Ebmaj7 is a natural movement and sounds better.
In the sixth line, playing Dbm7 after Dm7 continues the descending bass line theme.
In line seven playing B7#9 for the F7 continues the falling bass line theme.
In line eight, F#m7b5/A subs for D7 and keeps the falling bass line going.
So from line five on you end up with bass line of:
Eb,(Ab),D,Db,C,B,Bb,A.
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Food for thought, eh?