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A sharp (A#) is the note A raised by one semitone using a sharp (#). On the piano, A# is the black key immediately to the right of A.
What is A sharp?
In music theory, A# is a chromatic alteration of the natural note A. In the equal-tempered tuning system used by modern pianos, A# is enharmonically equivalent to B flat (Bb). This means that both notes sound exactly the same and are played on the same piano key.
Although A# and Bb have the same pitch, the correct name depends on the key signature and the harmonic context of the music.
How is A sharp used in piano playing?
Piano players encounter A# most often in keys such as B major and F# major. It may also appear as part of a chord or as a chromatic passing note between two nearby notes.
Learning to recognize that the same black key can be called either A# or Bb is an important step in understanding music theory, key signatures and chord spelling.