A prepared piano is a piano that has had its sounds temporarily altered by placing bolts, screws, mutes, rubber erasers, and/or other objects on or between the strings. Its invention is usually traced to John Cage's dance music for Bacchanale (c. 1938), created without room for a percussion orchestra. Typical of Cage's practice as summed up in the Sonatas and Interludes (1946–48) is that each key of the piano has its own characteristic timbre, and that the original pitch of the string will not necessarily be recognizable. Further variety is available with use of the una corda pedal.
When a properly prepared piano has been "unprepared", it should be impossible for anyone to tell that it had ever been prepared. Changes causing less easily reversible damage can be served by permanently dedicating an instrument, such as the tack piano.
Cage frequently cited Henry Cowell (1897–1965) as the primary inspiration for the prepared piano. Cowell pioneered piano extended techniques for what he dubbed "string piano", involving reaching inside the piano and pluck, sweep, scrape, thump, and otherwise manipulate the strings directly, rather than using the keyboard. He developed these techniques in numerous pieces such as Aeolian Harp (1923) and The Banshee (1925). Pieces of paper were called for in several early 20c works, the buzzing effect reminiscent of the parchment 'bassoon' pedal of early fortepianos. In his Ragamalika (1912–22), based on the classical music of India, French composer Maurice Delage (1879–1961) calls for a piece of cardboard to be placed under the B♭ in the second line of the bass clef to dampen the sound, imitating the sound of an Indian drum.
In his Chôros No. 8, a 1925 work for large orchestra, Heitor Villa-Lobos instructs the 2nd pianist to insert pieces of paper between the strings  Maurice Ravel's L'enfant et les sortilèges (1920-1925) calls for Luthéal, but allows piano with paper to substitute.
The invention of the "prepared piano", per se, is usually traced to John Cage. Cage first prepared a piano when he was commissioned to write music for Bacchanale, a dance by Syvilla Fort in 1938. For some time previously, Cage had been writing exclusively for a percussion ensemble, but the hall where Fort’s dance was to be staged had no room for a percussion group. The only instrument available was a single grand piano. After some consideration, Cage said that he realized it was possible “to place in the hands of a single pianist the equivalent of an entire percussion orchestra ... With just one musician, you can really do an unlimited number of things on the inside of the piano if you have at your disposal an exploded keyboard”.
Other composers, arrangers, performers, and compositions
- Ferrante & Teicher were an American piano duo who produced over a hundred albums of light classical and popular "easy listening" in their long careers (1947–1992). Between 1950 and 1980 they included partially prepared pianos on a number of their tunes to add percussive effects.
- On "All Tomorrow's Parties" from The Velvet Underground & Nico (1967), John Cale prepared his piano with a chain of paper clips.
- On his 1968 album Blues Roots, Dave Brubeck prepared a piano by laying copper strips across the strings to give the song "Blues Roots" a honky-tonk sound.
- Denman Maroney performs on what he has dubbed 'hyperpiano', which "involves stopping, sliding, bowing, plucking, striking and strumming the strings with copper bars, aluminum bowls, rubber blocks, plastic boxes and other household objects."
- Cor Fuhler pioneered many inside piano techniques during the 1980s and recorded his first prepared piano solo album 7CC IN IO on GeestGronden in 1995; recorded The Hands of Caravaggio with John Tilbury and M.I.M.E.O. on the USA label Erstwhile Records; and in 2007 he released Stengam on the French label Potlatch.
- Since 1982, Roger Miller has developed his own take on prepared piano in his work, initially on Mission of Burma's single "Trem II". Miller has since released many albums (on labels including Ace of Hearts, SST, New Alliance, Atavistic and Matador) incorporating this technique. His concert hall compositions since 2009 have often utilized prepared piano.
- On his 1975 album Another Green World, composer Brian Eno employed prepared piano on the track "Little Fishes".
- Hauschka, aka Volker Bertelmann, employed prepared piano techniques in his album The Prepared Piano in 2005.
- Several Aphex Twin compositions from the 2001 album Drukqs make use of prepared piano.
Strictly speaking, a tack piano is not a prepared piano,[according to whom?] since
- No objects are inserted into or onto the strings;
- The strings' original pitches remain perceptible; and
- The preparation is not fully reversible.
Although the tacks can be removed from the hammers, inserting them causes permanent damage to the felt; for this and other reasons, the use of tacks is generally discouraged by piano technicians.
The Acoustisizer is an electroacoustic musical instrument built from a small grand piano with built-in speakers, magnetic guitar pickups, PZMs, and prepared piano strings. It was built as part of a graduate thesis project at California State University Dominguez Hills by Bob Fenger (1983), a student of Richard Bunger (author of the Well Prepared Piano). Speakers are built into the bottom of the instrument, redirecting its own amplified sound back onto the sounding board, with strings and magnetic pickups creating an amplitude intensity loop, which in turn drives and vibrates suspended kinetic oscillators (assemblages of vibration sensitive materials). Secondary control parameters allow extraction of vibration and sound phenomena from the kinetic oscillators through a series of proximity microphones and PZMs (piezo-electric contact mics). An article by the inventor was published in Experimental Musical Instruments Magazine April 1991, Nicasio, California. It includes pictures of the kinetic oscillators and stages of the construction process, including an underbody view of the speaker system configuration.
- Ripin, Edwin M. , revised by Hugh Davies and Thomas J. Kernan (2013). "Prepared piano". In Root, Deane L. (ed.). The New Grove Dictionary of Music and Musicians. Oxford University Press.
- Bunger, Richard (1973). The Well-Prepared Piano. Colorado Springs: Colorado College Music Press
- Nicholls, David (1991 ). American Experimental Music 1890–1940. Cambridge, New York, and Melbourne: Cambridge University Press. (p. 523) ISBN 0-521-42464-X
- Bartók, Peter, Moses Asch, Marian Distler, and Sidney Cowell; revised by Sorrel Hays (1993 ): Liner notes to Henry Cowell: Piano Music (Smithsonian Folkways 40801). p. 12 (unpaginated)
- Pasler, Jann (2000). "Race, Orientalism, and Distinction in the Wake of the 'Yellow Peril'." In Western Music and Its Others: Difference, Representation, and Appropriation in Music, ed. Georgina Born and David Hesmondhalgh. Berkeley, Los Angeles, and London: University of California Press, p. 107.
- Prepared piano: 1915 edition at the International Music Score Library Project
- "Mettre des papiers entre les cordes" at figure 48, a passage doubled by harp. Chôros No. 8 (Villa-Lobos): Scores at the International Music Score Library Project
- Prepared piano: piano part at the International Music Score Library Project. the New Grove article cites this work in Edwin M. Ripin, revised by Hugh Davies and Thomas J. Kernan: "Prepared piano"
- Cage, John, and Daniel Charles (1981). For The Birds: John Cage in Conversation with Daniel Charles. Marion Boyers London. ISBN 0-7145-2690-8.
- Huey, Steve; Rovi. "Ferrante & Teicher Biography". CMT. Retrieved 28 October 2010.
- Mitchell, Tim Sedition and Alchemy : A Biography of John Cale, 2003, ISBN 0-7206-1132-6
- Liner notes from album Blues Roots (1968) by Gerry Mulligan and the Dave Brubeck Trio
- "Philadelphia FRINGE Festival 2000 - Hyperpiano". Archived from the original on 2007-12-31. Retrieved 2005-12-23..
- "7 CC in 10 - Cor Fuhler | Songs, Reviews, Credits". allmusic.com. Retrieved 2018-08-09.
- Pareles, Jon (1987-06-05). "Music: Roger Miller". The New York Times. Retrieved 2014-02-15.
- Burke, Kathleen (2012-06-19). "Fuse Feature: M2 — 'At Land's Edge' Album Review/Interview". ArtsFuse.org. The Arts Fuse. Retrieved 2014-02-15.
- Gottschalk, Jennie (2013-07-02). "The Mush Race of Boston: The SICPP 2013 Iditarod". NewMusicBox.org. New Music USA. Retrieved 2014-02-15.
- Tamm, Eric (1995). Brian Eno: His Music and the Vertical Color of Sound. Da Capo Press. p. 127.
In 'Little Fishes,' Eno plays prepared piano and Farfisa organ.
- "Hauschka | Album Discography | AllMusic". AllMusic. Retrieved 2017-07-14.
- "Hauschka". Discogs. Retrieved 2017-07-14.
- "WARP". warp.net. Retrieved 2018-03-15.
- Fenger, Bob Icon. "The Acoustisizer", Nicasio, California, volume 6, no. 6, April 1991.
- Fenger, Bob, "The Acoustisizer" "Archived copy". Archived from the original on 2013-12-02. Retrieved 2013-08-19.CS1 maint: archived copy as title (link) Joshua Tree, California, April 1991
- Bunger, Richard (1973). The Well-Prepared Piano. Colorado Springs: Colorado College Music Press
- Fürst-Heidtmann, Monika (1979). Das präparierte Klavier des John Cage. Gustav Bose Verlag Regensburg. ISBN 978-3-7649-2183-5.
- Dianova, Tzenka (2008). John Cage's Prepared Piano: The Nuts & Bolts. Mutasis Books Victoria. ISBN 978-0-9809657-0-4.
- 'Are You Prepared' 17-key Online Prepared Piano by Andreas Busk. Site includes free downloadable prepared piano sampler for Ableton Live, NI's Kontakt and Logic's EXS Sampler
- The Sound Collector - The Prepared Piano of John Cage by Tim Ovens (PDF version).
- If you build it, they will come! essay by Kyle Gann, includes video performance of preparation by Margaret Leng Tan (here).
- Prepared Piano Sample Set - By Tom Gersic. Some free, others cheap
- Prepared Piano Max/MSP-Object - By Dr. Stefan Bilbao, ported to Max/MSP by Thomas Resch
- Prepared piano demonstration and performance by Richard Bunger
- Epitonic.com: John Cage performed by Margaret Leng Tan, featuring In the Name of the Holocaust