A7-9 (A7b9) altered chord
Altered A chord for piano presented by keyboard diagrams.
Explanation: The A7-9 alter the A9 by the change of one note. The chord name can also be written as A7b9 or A7(b9).
Theory: The A7-9 are identical with the A9 except that the major ninth is flattenedThe tone is one half step lower.
Notes: A - C# - E - G - Bb