His choice of pentatonics is as follows:

For fast, complex songs like Giant Steps, simplify ii-V7-I into a single pentatonic scale that works over all 3 chords with no avoid notes. This is the major pentatonic of the V.

So, in Giant Steps with the following chords, you would play these pentatonics:

Bmaj: F# pent.
D7 Gmaj: D pent.
Bb7 Ebmaj: Bb pent.
Ebmaj: Bb pent.
A-7 D7 Gmaj: D pent.
Bb7 Ebmaj: Bb pent.
F#7 Bmaj: F# pent.
A-7 D7 Gmaj: D pent.
F-7 Bb7 Ebmaj: Bb pent.
C#-7 F#7 Bmaj: F# pent.

These are all major pentatonic scales, i.e. F# pentatonic is F# G# A# C# D#.

The cool thing about this is when you have a really fast song like Giant Steps, you can simplify to only 3 scales! Yes, that’s right, you can rip on the whole song with only F#, D and Bb pentatonic scales.

Mark Levine’s rule for more complex songs is this:

Over D minor 7, play either C major or G major pentatonic (same as A minor or E minor pentatonic).

Over G7, play G pentatonic or a substitution of it (tritone sub being most common: Db major pentatonic).

Using Barry Harris rules we can say the pentatonics to play over G7 are G, Bb, Db or E.

I guess it doesn’t matter if we play major or minor pentatonics then, because whichever we play, it will be a valid harmony over G7!

For C major 7, Mark Levine recommends the pentatonic from the fifth, G pentatonic. This yields a very pretty sound as it includes the 5, 6, 7, 9 and 3.

To recap:

D-7 C or G pentatonic
G7 G, Bb, Db or E pentatonic
Cmaj G pentatonic

He goes on to say that you play the pentatonic from the 4th over Melodic Minor harmony.

Here are some examples in the key of D melodic minor:

G7#11 G pentatonic
Here it is somewhat tame but balances the dissonance of the G7#11 chord.

D minor 6/9 G pentatonic
Played over a spicy D minor 6/9, G pentatonic makes a nice open consonant sound that contrasts with the tritone and half-step present in the chord. Since the scale contains neither tritone nor half-steps, it really stands out in stark relief against the tonality– a common trait of all pentatonics over Melodic Minor harmony.

E7sus4b9 G pentatonic
Boring sound here, I much prefer F major pentatonic (F G A C D). F pentatonic is an “out” sound and very very cool. If you get into the E7sus4b9 chords (typically played rootless as F-A-B-E with an E in the bass), then F pentatonic is a nice change of pace, especially because it doesn’t even include E as a note! But as for Mark Levine’s suggestion to use G pentatonic over E7sus4b9, I say it’s boring, don’t do it.

B-7b5 and others also sound good — basically anything in D melodic minor. Give it a try!

When you switch from E minor pentatonic to C minor pentatonic over an E minor chord, it could be argued that you are actually playing tritone substitution on a B7sus. The tritone of B is F, thus you could look at the C minor pentatonic as the 5, 7, 1, 2 and suspended 4th over an F7sus.

Barry Harris also has a rule of thumb which is that you can substitute any tension chord for chords diminished thirds away.

So, try playing the simple chord progression D-7 G7 Cmaj with this rule applied to the D-7 and G7. You can get some great reharmonizations this way!

Some examples:

D-7 | Bb7 | Cmaj
F-7 | Bb7 | Cmaj
F-7 | Db7 | Cmaj
Ab-7 | Db7 | Cmaj
Ab-7 | E7 | Cmaj
B-7 | E7 | Cmaj
B-7 | G7 | Cmaj

and so on….

Or you can try going the other direction:

D-7 | E7 | Cmaj
B-7 | E7 | Cmaj
B-7 | Db7 | Cmaj

etc …

Remember, all of these chord progressions (and their related scales) could be used a substitute for D-7 G7 Cmaj. It can be daunting to think of playing all these variations on all 12 keys, but when you remember the rule that you can substitute any tension chord for another of any quality minor 3rds away, it makes it easier.

The examples above are retaining the same quality of the chords but you can make it even more interesting by changing qualities, e.g. over the long D minor in So What you can try some interesting chord qualities by reharmonizing 2-5-1s in D minor:

D-7 | E-7b5 A7b9 | D-7 | E7 | F#7 | D-7 | Db-7b5 | Eb7 | D- ….