A♯, pronounced "A sharp," is a musical note that is one semitone higher than A and one semitone lower than B. It is represented on a piano keyboard as the black key immediately to the right of the A key. In music notation, A♯ is often used in various scales and chords, contributing to the overall harmony of a piece. In the context of Western music theory, A♯ can be found in several scales, including the A♯ major scale and the A♯ minor scale. It plays a crucial role in creating tension and resolution within compositions, making it an essential note for musicians and composers alike.