Chord sequence

Bm7, Bb7, Am7, Ab7

Bm7 B♭7 Am7 A♭7

Tempo 120 BPM

Rootless Shells Guide tones Rooted shells Rooted Drop 2

Four-note rootless voicings in their two forms, with the 3rd or the 7th on the bottom, played over the root.

Customize each chord

Bm7
Bb7
Am7
Ab7

Analysis

Heard in G major

Each chord's roman numeral and role in G major
Chord	Numeral	Role
Bm7	iii7	Diatonic
B♭7	subV7/ii	Tritone substitute for V7/ii
Am7	ii7	Subdominant
A♭7	?	Outside the key (bII7)

Progressions in these changes

All the chords

Chromatic iii-bIII-ii-bII Progression in G

The iii-VI-ii-V turnaround with both dominants replaced by tritone substitutes, so the roots descend by half steps from iii to I.

Scales to play