Prepared Piano is an invention by composer John Cage. He started putting all kinds of different objects into the piano in-between the strings and thereby changing its sound.
Screws, bolts, coins, erasers, jar rubber and plastic are all common materials and create a fantastic soundworld for the piano, which sounds more like percussion. A major work is the large scale cycle Sonatas and Interludes by John Cage, who wrote many pieces for the prepared piano. Tinna performed Sonatas and Interludes a.o. in a recital in the 15:15 series at The Reykjavík City Theatre in 2005 and here are some photos from the event. Tinna´s “kit” on this photo is still growing.