Sharp or flat is a term used to describe the pitch of a note in music. A sharp note is one that is higher in pitch than the note it is meant to represent, while a flat note is one that is lower in pitch. The SIGN for sharp is '#' and the SIGN for flat is 'b'. Offkey is a term used to describe when a note is not in tune with the rest of the notes being played. It is usually caused by a musician playing a note that is either too sharp or too flat.