什麼是PREPARED PIANO ?

A prepared piano is a piano which has had its sound altered by placing objects (preparations) between or on the strings or on the hammers or dampers.
The idea of altering an instrument's timbre through the use of external objects has been applied to instruments other than the piano; see, for example, prepared guitar.
History
John Cage was undoubtedly the composer who put the "prepared piano" concept on the world map, and coined the term. He credited Henry Cowell, and, to a lesser extent, Erik Satie, for contributing to the idea, and was probably unaware of many other precedents described below. Erik Satie prepared the piano for the performance of ‘Le Pige de Mduse’ (1913), a lyrical comedy considered to be the first example of surrealist drama. For its performance Satie put paper between the strings of the piano to create a mechanical effect.

圖片參考：http://upload.wikimedia.org/wikipedia/commons/thumb/b/bf/Christian_Wolff_prepared_piano_performance_2007_Feb.jpg/300px-Christian_Wolff_prepared_piano_performance_2007_Feb.jpg

My Own Advice

圖片參考：http://tw.yimg.com/i/tw/ugc/rte/smiley_23.gif
Please don't use some expensive pianos like Steinway& Sons/ to become a 'prepared piano' since using the above ways to use the piano improperly may cause damage!!
Some piainists may not accept the above ways to use the piano.
圖片參考：http://tw.yimg.com/i/tw/ugc/rte/smiley_28.gif