A prepared piano is a piano that 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, including the guitar and harp. Richard Bunger wrote a book ‘The Well Prepared Piano’ in which he explains how John Cage prepared his pianos and even which pianos are suitable, because of the deviation of string lengths within different brands.
Bunger also clarifies why the preparations were done in such ways; in other words, which adaptation creates which sounds (harmonics obtained, timbrel effects, etc.). The timbre of the instrument changes dramatically when preparations are introduced. Much of the technique is related to the harmonic positions of the strings. For instance a preparation on 1/2 of the string length causes a different sound than on 1/3. The preparations don’t cause a random sound, as is often assumed.
John Cage coined the term ‘prepared piano’ and was undoubtedly the composer who made the technique famous. He credited Henry Cowell and, to a lesser extent, Erik Satie, for contributing to the idea, but it is unclear if Cage was aware of many other precedents. Since the later days of the harpsichord (17th–18th century), stringed keyboard instruments could have registers (‘choirs’ of strings), for instance giving a drier or more ample sound when the instrument’s stop (e.g. foot pedal) was pulled. When the first pianos were invented around the beginning of the 18th century, the only ‘coloring’ of the sounds produced by the instrument resulted from how the individual keys were pressed (loud = forte, or softly = piano, giving the name to the instrument: fortepiano). A type of register, first implemented with a stop above the keyboard, which became a standard device for pianos in the second half of the 18th century, was engaging or disengaging the muting of the strings after the release of a key. Only by the end of the 18th century, the muting mechanism was triggered with a pedal, after an intermediate period when this register was operated by the pianist’s knees.
But the idea of harpsichord-like registers lived on: in the early 19th century some pianos were provided with a reed stop, which lowered a strip of paper onto the strings. This led musicologists such as Tom Beghin to believe that the technique of placing a strip of paper on piano strings would probably have originated before it was standardized as a register operated with stops, and that, for instance, Mozart’s ‘Alla Turca’ can safely be played with a piece of paper on some of the strings as a historical interpretation. Around the turn of the nineteenth century, Turkish music was so popular that piano manufacturers made special pianos with a Turkish stop, also called the military or Janissary stop. The player would press a pedal that caused a bell to ring and/or a padded hammer to strike the soundboard in imitation of a bass drum. The Turkish stop was popular for playing the famous Mozart ‘Rondo alla Turca, K. 331.’
The phrase prepared piano is also sometimes applied to other kinds of preparations. The tack piano is a piano that has been altered by inserting thumbtacks or small nails into the striking end of each hammer, so that the instrument will produce a more percussive sound and brighter timbre. The resulting tone often resembles the sound of a very old and derelict piano. The tack piano has been used primarily in honky-tonk-style piano playing, or to make a piano sound like an antique piano that might have been heard in a saloon or brothel around the early 20th century. The application of tacks is generally discouraged by piano technicians as the tacks can drop off the hammers and lodge in the strings or jam the mechanism, or the fact that placing tacks inside felt hammers renders the felt unvoicable and, therefore, ruins the hammers. On normal pianos, felt coverings on the hammers will harden and compress with use (though not usually for at least several decades, unless it is a heavily used concert piano), yielding a characteristic bright, tinny sound. This can be cured by softening the hammers with a device consisting of multiple needles called a ‘voicing needle.’ Where the felt is too far gone, the hammers can be replaced.
In the 1920s, American composer Henry Cowell coined the term string piano “to describe direct manipulation of piano strings, such as by plucking them with fingers or stroking them with a brush.
The Acoustisizer is an electro acoustic musical instrument built from a grand piano utilizing magnetic guitar pickups, speakers, and prepared piano strings to generate feedback sound noise effects. Built as part of a graduate project thesis at California State University Dominguez Hills in 1983 by Bob Fenger a student of Richard Bunger. Speakers are built into the bottom of the instrument redirecting its own amplified sound back onto the sounding board, 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 phenomenon from the kinetic oscillators through a series of proximity microphones and PZMs (piezoelectric contact mics).
John 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.’