Four-handed piano pieces are musical compositions that are written for two players to perform on one piano. The term 'four-handed' refers to the fact that two people are playing the same instrument. The most common type of four-handed piano piece is a duet, which is a composition for two players to perform together. Duets are typically written in two parts, with each part being played by one of the two performers. Four-handed piano pieces can range from simple melodies to complex works of art.