The Prepared Piano is a technique introduced in 1949 by John Cage, where objects like erasers, nails, wire, paper, etc., are inserted between a piano’s strings in certain places, causing them to produce additional tones, harmonics, or percussive sounds. For these recordings, a Bösendorfer grand piano was treated with all kinds of objects as well as with bare hands (e.g., glissandos over the strings) in order to create all-new, experimental, and sometimes scary sounds.