a keyboard is made up of five black notes and seven white notes forming one octave. each key relates to the pitch of that particular key and is equal to one semitone. the black keys raise or lower the pitch by one semitone. if they raise the pitch they are called sharps b. if they lower the pitch they are called flats b. so to the right of c is a raised black note called cb and the same note to the left of d is called db. because the black keys on the keyboard can be either sharps or flats depending on the key of the song or melody, they are sometimes referred to as enharmonic equivalents.