A Dominant Ninth Chord

Chord Tones: A Dominant Ninth Chord

Symbol: 9 — Formula: 1-3-5-♭7-9

Chord Notation

Roman numeral (e.g. I, IV, V) and Nashville Number notation are key-dependent. See Keys pages for chord function within specific keys.

Inversions

Harmonic Function

The A dominant ninth chord commonly functions as the submediant (vi) in C major or dominant (V) in D major. Its harmonic role varies by key — in major keys it provides stable harmonic grounding.

The dominant ninth chord extends the dominant seventh with a ninth, adding color and richness to one of music's most harmonically active chords. Essential in jazz, blues, and funk. The A Dominant Ninth Chord specifically contains 5 notes: A, C♯, E, G, B (formula: 1-3-5-♭7-9). On guitar, A-rooted chords anchor to the open A string (5th string), and barre chord shapes rooted on A form the basis of the "A-shape" CAGED system. Blues, rock, and country music use A-rooted chords extensively — the classic 12-bar blues often starts on A, and many rock power chord riffs center on the open A string.

Common Progressions

The A Dominant Ninth Chord frequently appears in these progression patterns (shown in Roman numeral notation relative to key):

• V9-I
• ii7-V9-I

Songs Featuring the Dominant Ninth Chord

Well-known songs where the A Dominant Ninth Chord — or this chord type — plays a prominent role:

• Purple Haze – Jimi Hendrix
• What's Going On – Marvin Gaye
• Superstition – Stevie Wonder

Tuning Frequencies Across Temperaments

Frequencies shown at A=440 Hz. View full temperament data for any note.

Scales Containing the A Dominant Ninth Chord

These scales include the A Dominant Ninth Chord as a diatonic or characteristic chord: