Diminished 7th (dim7)
Symmetric structure
Prove it — just do the practice exercise.
Bdim7 Root Position
B (R)D (♭3)F (♭5)Ab (°7)
The dim7 is built entirely from minor thirds:
• R – ♭3 – ♭5 – °7 (= 0, 3, 6, 9 semitones)
Symmetric: Any of the 4 notes can be the root. Only 3 distinct dim7 chords exist!
Example: Bdim7 = B + D + F + Ab
• R – ♭3 – ♭5 – °7 (= 0, 3, 6, 9 semitones)
Symmetric: Any of the 4 notes can be the root. Only 3 distinct dim7 chords exist!
Example: Bdim7 = B + D + F + Ab