A-sharp, also known as A♯, is a musical note that is one semitone higher than A and one semitone lower than B. It is commonly used in various musical scales and compositions, particularly in Western music. A-sharp can be represented on a piano keyboard as the black key immediately to the right of the A key. In terms of music theory, A-sharp is often found in the key signatures of B major and F♯ major. It plays a crucial role in creating melodies and harmonies, contributing to the overall sound and emotion of a piece. Musicians may encounter A-sharp in sheet music, where it is notated with a sharp symbol (♯) before the note.