A Major Ninth Chord

Chord Tones: A Major Ninth Chord

Symbol: maj9, M9, △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 major 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 major ninth chord extends the major seventh with a ninth, creating a lush, sophisticated sound central to jazz and R&B. It conveys spaciousness, warmth, and harmonic richness. The A Major 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 Major Ninth Chord frequently appears in these progression patterns (shown in Roman numeral notation relative to key):

• Imaj9-IVmaj9
• Imaj9-ii7

Songs Featuring the Major Ninth Chord

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

• Nights in White Satin – Moody Blues
• Clair de Lune – Debussy (adapted)
• Once in a While – jazz standard

Tuning Frequencies Across Temperaments

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

Scales Containing the A Major Ninth Chord

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