Chord & FretA#dim7 — diminished seventh
Also written Bbdim7 — the same chord, spelled the other way.
Notes in A#dim7: A# – C# – E – GFormula: 1 – b3 – b5 – bb7In the formula, the numbers count steps of the major scale starting from the note that names the chord; "b" lowers a half step, "#" raises one — and a slash names the bass note.
The diminished seventh stacks three minor thirds (1–b3–b5–bb7), forming a symmetrical and highly tense chord. It can stand in for a dominant with the root omitted.
The same chord on all four instruments
Where to use it: Between two neighbouring chords it acts as a half-step stair: in C → C#° → DmDmDmDm it is the little step that pushes the music forward. In practice it is a passing chord — you barely notice it, but you feel the motion.
The shapes of A#dim7 don't end on this page — the whole neck holds dozens. In Chord & Fret, you hear every shape strummed string by string, in each instrument's own voice; compare positions with their difficulty marked; and change the tuning — the shape rewrites itself. Start free. Unlock everything with Pro. Plays offline.
See the whole neck in Chord & Fret →Part of the Sevenths family.