He also would play directly on the strings of the piano, sometimes for the entire piano piece. The Banshee is one of these pieces. It takes two performers to play, one to play the strings, the other to hold down the pedal of the piano.
A Banshee is from Irish mythology, is female and appears as an omen of death and to bring messages from the other world. The Banshee begins to wail when someone is about to die.
Cowell directs the performer to wave their hands over the strings like a harp, to pluck the strings, to scrape their fingernails over the wound strings of the bass notes. It is for a grand piano, and the performer stands in the bend of the piano with their arms and shoulders inside the piano. Cowell brings out some very distinctive, different sounds from the piano, well suited to the subject of the piece.
Cowell's The Banshee, played by the composer: