A new digital musical instrument

The Rulers is a self-contained musical performance system called a digital musical instrument (dmi). This means that it includes a software synthesizer, a gestural interface to manipulate the software, and a stable mapping between the two (see the Wanderley paper listed below for more details). I completed the first design of the Rulers in 2004 as part of Stanford’s Summer music technology seminar. In 2006 it was outfitted with a USB port; in 2007 it underwent further design revisions to improve the physical interface; and in 2008 Stephen Sinclair greatly improved the sensor signal processing software. It premiered in Spring of 2008 at Pollack Hall in Montreal.


How it’s played

The instrument evokes the gesture of plucking or striking a ruler that is fixed at one end. Because the seven aluminum tines have different lengths, each tine oscillates for a different amount of time when struck. This provides an element of visual and haptic feedback to the player. The dampers and keystops, inspired by similar mechanisms in a piano, minimize the acoustic component of the tines’ oscillation. While they vibrate silently, their motion is sensed by infrared reflect sensors placed under each tine.

You can see and hear the Rulers being performed in this video. The Rulers can drive many different types of synthesizers, so their sound may vary depending on the composition. However, because the physical properties of the instrument remain consistent, so do the instrumental gestures that performers must use to play.

How it looks

The most striking visual aspect of the instrument is the artwork painted on the baseboard and keystops. During the Renaissance, many intricate works of art were painted directly on musical instruments.


Inspired by these beautiful instruments, like the harpsichord above which I encountered in the Musée de la Musique in Paris, I asked a prominent Montreal stencil artist to embellish the Rulers with a modern take on the old tradition.


How it sounds

Here’s the Rulers in “Sounds Between Our Minds” by D. Andrew Stewart, performed during the Music+Technology Incubator at CIRMMT in Montreal.

Further reading

Pestova, X., Donald, E., Hindman, H., Malloch, J., Marshall, M., Rocha, F., Sinclair, S., Stewart, D. A., Wanderley, M. M., Ferguson, S. The CIRMMT/McGill Digital Orchestra Project. In Proceedings of the International Computer Music Conference. Montreal, Canada, 2009.
Full text (pdf, 2.6 MB)

Pestova, X., Donald, E, Stewart, D.A. The Digital Orchestra Project: Digital musical instruments and performance practice. Presented at the Spark Festival of Electronic Music University of Minnesota, Minneapolis, MN, 2009.
Full text (pdf, 3.3 MB)

Malloch, J., Birnbaum, D., Sinyor, E., Wanderley, M. M. Towards a new conceptual framework for digital musical instruments. In Proceedings of the 9th International Conference on Digital Audio Effects, pp. 49-52. Montreal, Canada, 2006.
Full text (pdf, 336 KB)

Wanderley, M. M., Depalle, P. “Gestural control of sound synthesis.” In Proceedings of the IEEE Special Issue on Engineering and Music — Supervisory Control and Auditory Communication, vol. 92, no. 4, pp. 632–644, 2004.

Brum Medeiros, C., Wanderley, M. M. “Evaluation of sensor technologies for the Rulers, a kalimba-like digital musical instrument.” In Proceedings of the 8th Sound and Music Computing (SMC) Conference.
Full text (pdf, 1.8 MB)

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