A sharp is the symbol that raises a note by one semitone. It looks like a stylized number sign and is placed before the note head it affects. In a key signature, sharps indicate which notes are to be raised throughout the piece unless canceled.

Sharps appear frequently in keys on the right side of the circle of fifths. Players must keep the key signature in mind while also watching for additional sharps that occur as accidentals. On the keyboard a sharp usually means playing the black key to the right of the written note.

Together with the flat and the natural, the sharp forms the basic set of accidentals that allow notation of all twelve pitches within the octave. Accurate reading of sharps is essential for correct pitch in both tonal and chromatic music.

A single sharp can brighten a chord or intensify a melodic line.