What is it?

For over 50 years, composers and performers have been going inside of the piano to create new sounds. Continuing in the tradition of Cowell and Cage, performances which incorporate some manner of preparation are now common practice. With the advent of electronic technology, alterations to this acoustic instrument began fusing high-tech preparation methods as exemplified throughout the Twentieth Century - from Cahill's "Telharmonium" to the "Choralcello" to Yamaha's MIDI Disklavier. The Electromagnetically-Prepared Piano can be regarded as a middle ground between the traditional preparation of the acoustic piano and a fully electronic synthesizer. Materials are placed within the piano to alter it's natural voice, yet electronic sound synthesis methods primarily define pitch, and to some degree texture, of the acoustic response of the piano to its performer. While this manner of creating sound and music may or may not be novel, Voltaire, Cage, and others remind us: Il faut cultiver notre jardin.
By positioning a rack of transducers above the piano's strings - but never in physical contact with the strings - electromagnetic waves in the air gap create vibrations and sound from each of the piano's many naturally oscillating strips of steel. These transducers, a combination of electromagnets and permanent magnets, all connect to the soundcard output of a personal computer, where audio output signals can specified through any arbitrary software interface. The net effect, captivating as both a sound and an idea, is the ability to play the piano without felt hammers, plectrum, fingers, or any other traditional method of physical excitation. Notes can simply be played from the keyboard of a laptop.
As with other piano preparations, the range of sounds available to the pianist in some ways resemble the sound of the unprepared piano e forte, and in other ways is quite divergent. For example, by sending a sine wave signal from a computer to the A4 string (440 Hz), the string will vibrate at this naturally resonant frequency. A sustained tone will eminate as long as the electrical signal endures, and will be shaped by the contours of the piano string and body, in a manner analogous to filtering. What is especially exciting about this method of vibrating the string is the ability to send virtually any sound wave into a string. In the previous example, one could send another sine wave into the same A4 string, but at a frequency of 880 Hz. The resultant tone will then be an octave higher than that heard from pressing the A4 piano key normally. Having the option to isolate partials on each string and combine them in different ways opens up new pathways to timbral expression previously available to the pianist in some degree, but typically regarded as a synthesis method of the electronic musician. One might call this speakerless acousmatic synthesis. The most recent incarnation of the instrument consists of twelve independent channels (i.e. twelve transducers over twelve different notes). When played in combination, the instrument bears striking resemblence to a church organ, but with strings!







Steven Backer

Stanford University

Center for Computer Research
in Music and Acoustics