Diminished 7th
Bb°7 is a diminished chord rooted on Bb. It creates intense tension and instability, functioning as a leading tone chord or a passing chord in jazz harmony. The half-diminished (m7b5) is the most common form, serving as the ii chord in minor key ii-V-i progressions (Levine, The Jazz Theory Book).
26 voicings · diminished
Left Hand
Right Hand
Left Hand
Right Hand
Left Hand
Right Hand
Left Hand
Right Hand
Left Hand
Right Hand
Melody (G5) doubled an octave below (G4) with chord tones in between
Left hand alternates between bass note and chord
Beat 1 & 3 — Bb3
Beat 2 & 4 — Db, E, G
Left hand alternates between bass note and chord
Beat 1 & 3 — F3
Beat 2 & 4 — Db, E, G
The half-diminished chord (also written as Bbø7) functions as the ii chord in minor keys — it is to minor keys what the minor seventh is to major keys (Mulholland & Hojnacki, The Berklee Book of Jazz Harmony). Fully diminished seventh chords function as passing chords or dominant substitutions. Levine notes that the half-diminished is one of the most misunderstood chords in jazz — it needs to be voiced carefully to avoid harshness (The Jazz Piano Book).
Half-diminished chords pair with the Locrian mode or, more commonly, Locrian #2 (the sixth mode of melodic minor). Fully diminished chords use the whole-half diminished scale (Aebersold, Jazz Handbook).
Half-diminished chords typically resolve to a dominant seventh chord a fourth above (in minor ii-V-i). Fully diminished chords resolve up a half step (Levine, The Jazz Theory Book).
Minor ii-V-i
Bb°7 as the ii chord in a minor key ii-V-i
Passing diminished
Connecting two diatonic chords a whole step apart
Turnaround
iii-VI-ii-V with Bb°7 as the ii
Bb°7 is a diminished chord built on Bb with a flattened fifth. In jazz, this chord most commonly appears as the ii chord in minor key progressions (Levine, The Jazz Theory Book).
Shell voicings work well: root, b3, b5, b7. Rootless voicings are also effective. Mantooth recommends practising minor ii-V-i progressions to build fluency with half-diminished voicings (Voicings for Jazz Keyboard).
The half-diminished chord is the starting point of the minor ii-V-i progression — learning to voice it smoothly is essential for playing in minor keys.
— Mantooth, Voicings for Jazz Keyboard
Locrian #2 (from melodic minor) is preferred over natural Locrian because the raised second avoids a minor ninth interval above the root.
— Levine, The Jazz Theory Book, pp. 56-58