The Electromagnetically-Prepared Piano
Developed by Per Bloland in collaboration with Steven Backer, Ed Berdahl,
Andrew McPherson, and the Instrumentation Lab at Miami University.
The Electromagnetically Prepared Piano (EMPP) device consists of a rack of twelve electromagnets which rests on the frame of a grand piano. Each individual electromagnet unit is positioned directly over the two or three strings that constitute a single pitch. The system is in many ways similar to an EBow, however each electromagnet is controlled by an arbitrary external audio signal, resulting in a much higher degree of control over pitch and timbre. This signal can originate from any source and consist of anything. In addition to its own fundamental, any string can be excited quite effectively at any of its first twenty or so partials. However the capabilities of the electromagnets are by no means restricted to excitation of individual overtones of the strings. For example it is possible to create glissandi, or to send a single source signal to all twelve electromagnets. In fact any sound can be reproduced to some degree, though it will be heavily colored by the piano.
The development of the EMPP has occurred in three stages:
Version 1: Developed 2005-6 at Stanford University’s Center for Computer Research in Music and Acoustics (CCRMA) by myself (Per Bloland), Steven Backer, and Edgar Berdahl. See here for Steven Backer’s original documentation of this project.
Version 2: In 2012 several enhancements were made to allow for a more powerful signal and easier installation. A new amplifier circuit board was designed by Andrew McPherson, and a new rack and a new electromagnet-height adjustment mechanism were designed by the Instrumentation Lab at Miami University (details).
Physical Model (version 3?): As a result of a Musical Research Residency at IRCAM in 2013, a physical model of the interaction between an electromagnet and a resonating body was developed. This interaction was incorporated into Modalys, IRCAM’s physical modeling software. The project was undertaken in collaboration with Joël Bensoam, Robert Piéchaud, and the Instrumental Acoustics Team. For more information see here.