Unsounding Objects

A percussion instrument which uses everyday objects to control sound synthesis

Rice flying everywhere!
Zachary Hale throws a handful of rice into a bowl during a performance at the live@CIRMMT concert series. Photo ©Harold Kilianski.

As a contemporary percussionist it is great fun to explore the sounds and forms of everyday objects in the world around us. Many contemporary compositions explicitly call for percussionists to assemble their own collection of such “found” objects. At the same time there is also a growing interest in bridging the gap between our physical interactions with the world and the vast sonic worlds provided by computer-based sound synthesis. Unsounding Objects makes it possible for percussionists to control these kinds of synthesis while performing with found objects.

Playing objects on a metal pan with bamboo skewers.
A collection of objects on one of the playing surfaces. Each object’s unique timbre provides a different sonic response.

To accomplish this we created an interface we call the Spectrasurface. Built into a vintage suitcase, the Spectrasurface consists of four playing surfaces, each with its own audio transducer on the underside. When an object is placed on a surface and struck its sound is picked up by the transducer and sent to a computer to be analyzed in real-time. The result of the analysis is a set of control signals which can be used to control sound synthesis or other algorithmic processes.
Performing with the Spectrasurface not only enables the control of a wide variety of sounds, but it also affords a great deal of flexibility in terms of playing techniques. Enabling performance techniques which build on embodied experience and interaction with physical systems was extremely important to us, as these approaches are central to contemporary and experimental percussion performance. In order to explore the possibilities Preston Beebe composed two studies for the Spectrasurface in which the performer rolls marbles in bowls, runs their hands through piles of rice, throws rice into a bowl, and strikes glass plates with bamboo skewers.

How to create digital sound from everyday objects

When you strike an object it generates a distinct sound which is a manifestation of a collection of audio frequencies whose volume changes over time. Which frequencies are audible can vary greatly depending on how an object is struck, rubbed, scratched, damped, etc. Percussionists are experts at this kind of interaction, with a knowledge of how to evoke widely varying timbres from different objects.

Once the sound is sent to the computer we can analyze it to determine its important sonic characteristics, or “audio features”. Simple examples include estimates of a sound’s brightness or noisiness, while more complex algorithms may attempt to classify the physical properties of the object which created the sound.

In Unsounding Objects we utilize audio features which balance descriptive power with computational efficiency. This enables the instrument to create sounds which are an immediate and powerful response to the performer’s gestures.

Further Applications of Audio Feature Extraction

Intimate control of timbre isn’t limited to percussionists, of course, and we have experimented with applying the techniques behind Unsounding Objects to a variety of other instrument formats. In particular, we are interested in combining this approach with more common techniques such as the use of keys, dials, and sliders. While these controls provide direct access to synthesis parameters the use of audio feature extraction reintroduces the subtleties of physical interaction with acoustic systems to the performance of electronic and digital music.

Pictures demonstrating four ways of interacting with the Spectrasurface
The Spectrasurface can be played with a variety of techniques. Some possibilities (clockwise from top left): dropping rice into a bowl, rolling a marble in a bowl, using sticks on cymbals , and dragging a bowl on top of a playing surface.


Credits

Ian Hattwick: Hardware and Software Design, Programming
Preston Beebe: Composition and Software Design
Zach Hale: Performance and Software Design

Publications

Hattwick, Ian, Preston Beebe, Zach Hale, Marcelo M. Wanderley, Phillippe Leroux, and Fabrice Marandola (2013). “Unsounding Objects: Audio Feature Extraction for Control of Sound Synthesis in a Digital Percussion Instrument”. In: Proceedings of the International Conference on New Interfaces for Musical Expression. London, England, pp. 597-600.
Abstract and Download

Acknowledgements

Funding provided by two CIRMMT Student Awards, and the CIRMMT Director’s Prize for Interdisciplinary Research.

Performances

July 1, 2015  – New Interfaces for Musical Expression (NIME)
, Goldsmiths Great Hall, University of London, England
March 22, 2014 – Digital Composition Studio Concert, 
Schulich School of Music, McGill University, Montreal, Canada
November 13, 2013 – Percussive Arts Society International Convention (PASIC)
, Indiana University Purdue University, Indianapolis, USA
June 13, 2013 – Mathematics and Computation in Music Conference, 
McGill University, Montreal, Canada
May 23, 2013 – CIRMMT Student Symposium, 
Centre for Interdisciplinary Research in Music Media and Technology, Montreal, Canada
April 30, 2013 – Coast x Coast Récital-Conférence Électroacoustique
, Canadian Music Centre, Montreal, Canada
February 07, 2013 – live@CIRMMT Concert Series: New Instruments