A9 piano chord — the keys, the inversions, the theory

A9 is a ninth chord built from A, C#, E, G, B. Below: the keys to press, every inversion with its own diagram, the intervals it is made of, the keys whose scale contains it, and a progression that actually uses it. Press any diagram to hear it.

A9

A · C# · E · G · B

Piano keyboardC4C5

Semitones above the root: 0 – 4 – 7 – 10 – 14

A major third with a flattened seventh above it: unstable on purpose, and it wants to resolve a fourth up.

Inversions of A9

  • Root position

    A · C# · E · G · B · bass A

  • Inversion 1

    C# · E · G · A · B · bass C#

  • Inversion 2

    E · G · A · B · C# · bass E

  • Inversion 3

    G · A · B · C# · E · bass G

Same chord, different note at the bottom. Press a diagram to hear it — inversions are how you move between chords without jumping your hand across the keyboard.

Keys that contain A9

  • DV

In D it does this job: I – V – vi – IV

  1. D
  2. A9
  3. Bm
  4. G

Questions