The Digital Baton, built in 1996 and used in the Brain Opera performances, is a multimodal musical input device, which measures fine position over a limited range, gross motion over infinite range, and finger pressure. A small microprocessor in the baton samples signals from 5 pressure-sensitive resistors potted into the baton skin (to measure finger and hand pressure) and 3 orthogonal accelerometers in the baton base (to measure sweeping gestures and beats). These signals are sent through a wire to the host computer running ROGUS. A camera housing a position-sensitive photodiode looks at an infrared LED mounted at the baton tip. This camera is only sensitive to the 20 kHz signal emitted from the LED; all other light sources are ignored. The photodiode in the camera directly produces a signal that determines the horizontal and vertical coordinates of the baton tip; no video processing is required. A bright red LED is also potted into the baton body near the tip; the intensity of this LED can be varied under MIDI control for visually expressive purposes (it serves only aesthetic function). See here for an older (1995) conceptual implementation of the Digital Baton, which was actually built as our first prototype. The 1996 Digital Baton, used in over 100 worldwide performances, can be seen in this photo. Link here for more explanation and demo videos.
The Brain Opera Technology: New Instruments and Gestural Sensors for Musical Interaction and Performance Joseph Paradiso. Journal of New Music Research, Vol. 28, No. 2, 1999, pp. 130-149.
Marrin, T. and Paradiso, J., "The Digital Baton: a Versatile Performance Instrument," Proc. of the 1997 International Computer Music Conference, Thessaloniki, Greece, September 1997, pp. 313-316.
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