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 and therefore can play seven notes per octave. Smaller harps, often called folk, lever or Celtic harps, also have only seven strings per octave, and use a mechanical lever on each string that the player must move manually for chromatic alterations. The only completely chromatic harps are the double (arpa doppia) and triple (Welsh) harps and cross-strung harp.