Tritone (of next chord) | CMaj7 - A♭7 | Dm7 |
First look at the plain progression...
Original Chord Progression | CMaj7 | Dm7 ||
...to that the passing chord is added (generically I call it "?")
Original Chord Progression | CMaj7 ? | Dm7 ||
A♭7 fills in the
? as the passing chord. It's root
A♭ is a tritone away from the target chord
Dm7. (This is not a case of tritone substitution, another jazz harmony idea, the similar naming could be confusing.)
The author is coy about the voicing of the passing chords...
Note: That both the chord and the bass-line movement are important when transitioning between chords. You want both to be smooth. I will have more to say about this in future lessons.
A very quick review of the chart shows all the passing chords can be voiced so that the bass will either be a common tone with one of the two chords of the simple two chord progression or a chromatic half step between them. All other voices should move the minimal distance.
All the basses probably should be:
Approach #1 (diatonic) | CMaj7 - Em7 | Dm7 ||
...where the bass should probably be
C D D
I'm taking an approach the bass of the passing chord should not anticipate (be the same tone) as the bass of the target chord.