Diminished seventh
Three stacked minor thirds. Fully symmetric, so it bridges several keys at once.
Symbol °7 · C°7 Four notes
Listen
Notes of the chord
1 C m3 E♭ ♭5 G♭ dim7 B𝄫
C A
Where you have heard it
Modulações and chromatic passages
What it gets confused with
Frequently asked
Which notes make a diminished seventh chord?
Three stacked minor thirds — for example B, D, F and A flat.
Why can it resolve almost anywhere?
It is symmetric: every inversion sounds the same, so it can be read as belonging to several keys at once.
Where does it turn up?
In modulations and chromatic passages, exactly because of that ambiguity.
There is an exercise track dedicated to recognising this by ear.
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