A Dominant 9th

A9

Notes

A · C# · E · G · B

Intervals

  • RootA (1P)
  • Major 3rdC# (3M)
  • Perfect 5thE (5P)
  • Minor 7thG (7m)
  • Major 9thB (9M)

Fretboard

EBGDAE357912EGABC#EBC#EGABGABC#EGEGABC#ABC#EGAEGABC#E

About

The A9 dominant ninth (A–C♯–E–G–B) extends a dominant 7 with a ninth. The B adds brightness and harmonic richness without affecting the chord’s dominant function — the tritone between C♯ and G is still present and still drives resolution to D. The 3rd and ♭7 remain essential; the 5th is routinely dropped on guitar to make room for the 9th without creating a muddy cluster. Common in funk, jazz, and blues as a more colorful version of the dominant 7. Compared to A7, the 9th adds shimmer and modernity; the resolution tendency is identical.

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