THE ELECTROMAGNETICALLY-PREPARED PIANO AND ITS
COMPOSITIONAL IMPLICATIONS
Per Bloland
Stanford University
Music
ABSTRACT
The Electromagnetically Prepared Piano device allows
for direct control of piano strings through the use of an
array of electromagnets. Created recently at Stanford
University's Center for Computer Research in Music and
Acoustics (CCRMA), the EMPP differs significantly
from previous instruments based on similar principles in
that each magnet is controlled by an arbitrary external
audio signal, resulting in a much higher degree of control
over pitch and timbre. The resultant sounds range from
simple sine tones through complex, often ethereal
textures. For the most part, these timbres are more
evocative of electronically synthesized sonorities than of
the acoustic piano strings from which they emanate. This
paper has three primary goals: 1) to examine the
compositional implications of such a hybrid instrument,
2) to describe several of the compositions that have
utilized the device, and 3) to provide a detailed
mechanical description for others who may wish to
experiment with such a device.
1. INTRODUCTION
A previous paper [1] has already described many of the
technical aspects of the electromagnets and their
interactions with metal strings. This paper will take a
more compositionally oriented approach, describing
some of the resulting timbres and the roles they have
played in several compositions, and discussing practical
issues of implementing and utilizing such a device. In
doing so, the author hopes to describe in more general
terms the applications to which the electromagnets have
been applied thus far.
2. HISTORICAL CONTEXT
The idea of using electromagnets to resonate piano
strings is by no means a new one. In fact the first
instance of such a system occurs as far back as 1886,
with Richard Eisenmann of the German firm
Electorphonisches Klavier. Through the use of
electromagnets positioned near the strings, Eisenmann
produced an infinitely sustaining note [2].
More recently, Alvin Lucier has experimented
rather extensively with the use of electromagnets to
resonate strings. For Music on a Long Thin Wire (1977),
a single segment of piano wire is stretched over two
bridges. A large horseshoe magnet straddles this wire on
one end, and the system is controlled with sine waves
passed through a power amplifier [3]. In Music for Piano
with Magnetic Strings (1995), Lucier updates this
concept by incorporating EBows. These small handheld
devices, familiar to many electric guitarists, allow the
guitar to sound with no attack and with infinite sustain.
In his piece, Lucier calls for several of these devices to
be held over piano strings. Rather than using standard
musical notation, the score provides a text description of
the desired resultant sounds [4]. Whereas the first piece
has a raw, "sinusoidal" quality, in the second the use of
multiple strings, the fact that they remain within the
body of a piano, and the mechanism of the EBow all
serve to create a smoother sound with a richer overtone
content. In addition, Lucier's use of a handheld device
such as the EBow opens the possibility of augmenting
the pure resonant sound by bringing the device into
physical contact with the vibrating string.
3. ORIGINS
The use of resonant piano strings was first explored by
the author in a piece for solo trumpet, entitled
Thingvellir (2001). In this piece, the performer is
instructed to play the trumpet into a microphone which
feeds a loudspeaker placed beneath a grand piano. If the
damper pedal on the piano is held down, the strings then
resonate sympathetically with the projected sound of the
trumpet. In addition, the piano itself is amplified in order
to provide a better balance between the resonating
strings and the acoustic trumpet. A similar approach is
taken by Luciano Berio in his piece Sequenza X (1984),
also for trumpet, in which the performer is periodically
required to blast notes into a piano while another
performer holds down specified keys. Thingvellir
focuses more directly on the resonant potential of the
strings in that the entire first half of the piece is
performed into the piano, and all the strings are free to
resonate.
After initial experiments with Thingvellir, the
desire for more direct control over the vibrating string
led to the idea of incorporating electromagnets. The
author, Steven Backer, and Ed Berdahl, both of
CCRMA, began the design process in the early months
of 2005. One of the first decisions involved the number
of electromagnets to build. Though full coverage of the
piano had its appeal, the creation of eighty-eight
individual electromagnets was deemed both unrealistic
and unnecessary. It became clear that twelve would be
sufficient, thus allowing for full coverage of the
chromatic scale should that be desired.
4. DESCRIPTION
4.1. Physical description
The twelve electromagnets are attached to a rack that is
secured to the piano frame, and each electromagnet is
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