 Pedal harps are essentially diatonic instruments with the double-action pedal mechanism providing chromatic alterations and key changes.No matter how the pedals are set, the pedal harp still has only seven strings per octave.Smaller harps, often called folk, lever or Celtic harps, are equally diatonic, with seven strings per octave, and use a mechanical lever on each string that the player must move manually for chromatic alterations.