Passing Diminished Chords

Passing Diminished Chords move between two diatonic posts, with a root motion of half-steps. They can ascend or descend, forming a three-chord cluster.

Passing Diminished Chords
examples in C major
Three-Chord Cluster	Roman Numeral Analysis
ascending
C^maj7 C#^o7 Dm⁷	I^maj7 # I^o7 IIm⁷
Dm⁷ D#^o7 Em⁷	IIm⁷ # II^o7 IIIm⁷
Dm⁷ D#^o7 ^C/_E	IIm⁷ # II^o7 ^I/_3rd
F^maj7 F#^o7 G	IV^maj7 # IV^o7 V
F^maj7 F#^o7 ^C/_G	IV^maj7 # IV^o7 ^I/_5th
G G#^o7 Am⁷	V # V^o7 VIm⁷
^C/_G G#^o7 Am⁷	^I/_5th # V^o7 VIm⁷
Am⁷ A#^o7 ^G/_B	VIm⁷ # VI^o7 ^V/_3rd
Three-Chord Cluster	Roman Numeral Analysis
descending
^G/_B Bb^o7 Am⁷	^V/_3rd bVII^o7 VIm⁷
Am⁷ Ab^o7 G	VIm⁷ bVI^o7 V
Am⁷ Ab^o7 ^C/_G	VIm⁷ bVI^o7 ^I/_5th
G Gb^o7 F^maj7	V bV^o7 IV^maj7
^C/_G Gb^o7 F^maj7	^I/_5th bV^o7 IV^maj7
Em⁷ Eb^o7 Dm⁷	IIIm⁷ bIII^o7 IIm⁷
^C/_E Eb^o7 Dm⁷	^I/_3rd bIII^o7 IIm⁷
Dm⁷ Db^o7 C^maj7	IIm⁷ bII^o7 I^maj7

All allowable tensions on each diminished chord are diatonic to the key, and all scales for each diminished chord contain all four chord tones of the chord. They are also presented as functional scales, meaning they are rooted to the key, not to the chord. These scales are eight-note scales, giving diminished chords a passing tone between all four chord tones, including the 7th and the root.

Passing Diminished Chords
all examples in C
chord	chord tones	tensions	scale
ascending
C#^o7 # I^o7	C# - E - G - Bb	A - C b13 - b15	C - C# - D - E - F - G - A - Bb - C C mixolydian add #1
D#^o7 # II^o7	D# - F# - A - C	B - D b13 - b15	C - D - D# - E - F# - G - A - B - C C lydian add #2
F#^o7 # IV^o7	F# - A - C - Eb	B - D - F 11 - b13 - b15	C - D - Eb - F - F# - G - A - B - C C jazz minor add #4
G#^o7 # V^o7	G# - B - D - F	E - G b13 - b15	C - D - E - F - G - G# - A - B - C C ionian add #5
A#^o7 # VI^o7	A# - C# - E - G	A b15	C - C# - D - E - F - G - A - A# - B - C C ionian add #1, #6
chord	chord tones	tensions	scale
descending
Bb^o7 bVII^o7	Bb - Db - E - G	C - A 9 - b15	C - Db - D - E - F - G - A - Bb - C C mixolydian add b2
Ab^o7 bVI^o7	Ab - B - D - F	E - G b13 - b15	C - D - E - F - G - Ab - A - B - C C ionian add b6
Gb^o7 bV^o7	Gb - A - C - Eb	B - D - F 11 - b13 - b15	C - D - Eb - F - Gb - G - A - B - C C jazz minor add b5
Eb^o7 bIII^o7	Eb - Gb - A - C	F - B - D 9 - b13 - b15	C - D - Eb - F - Gb - G - A - B - C C jazz minor add b5
Db^o7 bII^o7	Db - E - G - Bb	A - C 11 - b15	C - Db - D - E - F - G - A - Bb - C C mixolydian add b2

There is also a I^o7 chord which resolves to a I^maj7 chord (oblique motion), and Approach Diminished Chords, which ascend or descend by half-step to a diatonic target. All chords listed here as passing diminished chords can also function as approach diminished chords.