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A flat (Ab) is the note A lowered by one semitone using a flat (b). On the piano, A flat is the black key immediately to the left of A.
What is A flat?
In music theory, A flat is a chromatic alteration of the natural note A. In the equal-tempered tuning system used by modern pianos, A flat (Ab) is enharmonically equivalent to G sharp (G#). This means that both notes have the same pitch and are played on the same piano key.
Although Ab and G# sound identical, the correct name depends on the key signature and the harmonic context of the music.
How is A flat used in piano playing?
A flat is a common note in keys such as A flat major, E flat major and D flat major. It also appears frequently in jazz, blues and popular music.
Learning to recognize that the same black key can be called either Ab or G# is an important part of understanding key signatures, scales and chord spelling.