The random pedal technique was introduced by Luciano Berio in his Sequenza II for solo harp in 1963.
The harpist plays a sequence of notes and at the same time moves one or two pedals rapidly and continuously. The pedals affect the played notes randomly.
The movement of the pedals is very audible and creates a continuous back and forth sound between the pitches the pedals control.
The movement of the pedals is indicated below the relevant passage in the following manner:
Pedals moving in the same direction between all three pedal positions.
The random pedal passage ends on the pedal setting that is relevant for the next passage.
The pedals can be moved in the same direction, as in the example above, or in the opposite direction. They can also move through all three different pedal positions or only between two positions.
Pedals moving in the opposite direction between two pedal positions.
If two pedals are used simultaneously, then they must be on opposite sides of the harp. See: pedal mechanism.
The whole harp.
The random pedal technique is often used in combination with bisbigliando or with other repeated and/or random note patterns.