The Hyperbow: A Precision Violin Interface
Diana Young
Media Lab, MIT
email:diana@media. mit. edu
Abstract
This paper addresses the need to utilize precision measurement techniques in the the creation of new performance instruments and interfaces. Discussed within is
the design and construction of a new violin interface,
the Hyperbow, which serves as a first demonstration of
how a violin bow might be made capable of measuring
the most intricate aspects of violin technique-the subtle elements of physical gesture that immediately and
directly impact the sound of the instrument while playing. In order to provide this insight into the subtleties
of bow articulation, a sensing system has been integrated into a commercial carbon fiber bow to measure
changes in position, acceleration, and the downward
and lateral strains on the bow stick. These sensors
were fashioned using an electromagnetic field sensing
technique, commercial MEMS accelerometers, and foil
strain gauges. The measurement techniques used in
this work were found to be quite sensitive and yielded
sensors that were easily controllable by a player using
traditional right hand bowing technique.
1 Introduction
Though a great deal of progress has been made in
the fields of audio analysis and synthesis, and software tools for musicians continue to quickly increase,
there is comparatively little advancement in the area of
performance instrument design and development, especially for accomplished players. Certainly, there is a
great need for the development of new musical interfaces that may respond to the smallest and most subtle
gesture of an accomplished musician. Not only may
much be learned from accessing this level of description of musical technique, but by using this data we
may begin to delve into new kinds of musical expression, building upon traditional methods of manipulating sound. Of course, care must be taken not to reduce
the playability of the instrument in the development of
such an interface. As in the study of a violin bow interface described here, when beginning with a traditional
acoustic instrument as a model, this issue is of extreme
importance.
The violin (and its accompanying bow) is a prime
candidate for study and evolution. Traditional violin
repertoire and technique require extremely subtle articulations and sophisticated coordination of gesture,
most of which is not easily understood by non-players.
For these reasons, the violin is a source of inspiration
for new music controllers.
The problem of how to develop a new musical interface for an experienced string player in order to create
new methods of musical expression was addressed in
the Hypercello and subsequent Hyperinstruments work
at the M.I.T. Media Lab (Paradiso and Gershenfeld 1997;
Machover 1992). Later, projects such as the bossa (Princeton) were developed (Trueman and Cook 1999). These
endeavors used measurements such as bow position,
pressure on the bow stick, and acceleration of the bow
to alter the sound produced by the bowed string.
The Hyperbow project discussed in this paper is a
music controller similar to those mentioned above, as
the sensing system on which the controller is based includes sensors for bow position and acceleration (Young
2001). However, in order to provide greater insight into
the subtlety of gesture demanded of and used by violinists, different types of strain in the bow stick are
also measured. The downward and lateral strains on
the bow stick are closely related both to the experience of a violinist while playing and to the immediate changes in the sound produced by the string when
bowed. The three sensing subsystems-position, acceleration, and strain-were grafted onto a carbon fiber
bow to enable (directly or indirectly) the Hyperbow to
collect and transmit data reflecting bow position, speed,
acceleration, downward force, and angle of the bow.
This paper describes the implementation and design considerations of the Hyperbow project, applications, and future advancements.
2 Design and Implementation of the
Hyperbow
2.1 Position Sensing
The method of sensing the position of the bow (relative to the bridge of the violin) presented in this paper
is an adaptation of the system used in the development
of the Hypercello (Paradiso and Gershenfeld 1997).
In this method, two square wave signals of different
frequencies are produced. The signals are connected to
opposite ends of a resistive strip that spans the length
of the bow. A simple electrode antenna is placed behind the bridge of the violin. This antenna is connected
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