C9 piano chord — the keys, the inversions, the theory

C9 is a ninth chord built from C, E, G, Bb, D. 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.

C9

C · E · G · Bb · D

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 C9

  • Root position

    C · E · G · Bb · D · bass C

  • Inversion 1

    E · G · Bb · C · D · bass E

  • Inversion 2

    G · Bb · C · D · E · bass G

  • Inversion 3

    Bb · C · D · E · G · bass Bb

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 C9

  • FV

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

  1. F
  2. C9
  3. Dm
  4. Bb

Questions