Design of a Helical Keyboard

Jens Herder and Michael Cohen
University of Aizu 965-80

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Inspired by the cyclical nature of octaves and helical structure of a scale (Shepard, '82 and '83), we prepared a model of a piano-style keyboard (prototyped in Mathematica), which was then geometrically warped into a left-handed helical configuration, one octave/revolution, pitch mapped to height. The natural orientation of upper frequency keys higher on the helix suggests a parsimonious left-handed chirality, so that ascending notes cross in front of a typical listener left->right. Our model is being imported (via the dxf file format) into (Open Inventor/)VRML, where it can be driven by MIDI events, realtime or sequenced, which stream is both synthesized (by a Roland Sound Module), and spatialized by a heterogeneous spatial sound backend (including the Crystal River Engineering Acoustetron II and the Pioneer Sound Field Control speaker-array System), so that the sound of the respective notes is directionalized with respect to sinks, avatars of the human user, by default in the tube of the helix. This is a work-in-progress which we hope to be fully functional within the next few months.

Alternative coloring schemes:

Besides the traditional ebony & ivory, alternative coloring schemes include a color wheel (below left), wireframing of white keys for visualization of pentatonic music, and a dynamic color map (below right) compatible with chromastereoptic eyewear.

Discontinuous (spiraling) color wheel
(color-complementing traditionally black keys)
Chromastereoptic rendering

Octave normalization through multiple sinks:

Our system is designed to allow separate audition of harmony and melody, traditionally played by the left and right hands, respectively, on a normal keyboard. A single head inside the helix, near its base for instance, might easily distinguish the position of the harmony, but the melodic notes would all seem to come from the upper pole.
Perhaps the most exotic feature of the helical keyboard is the ability to fork one's presence (Cohen, '95; Cohen and Koizumi, '95), replicating subject instead of object, by installing multiple sinks at arbitrary places around the virtual scene so that, for example, harmony and melody can be separately directionalized, using two heads to normalize the octave; such a technique effectively doubles the helix from the perspective of a single listener. Rather than a symmetric arrangement of the individual helices, we perceptually superimpose them in-phase, coextensively, so that corresponding notes in different octaves are at the same azimuth. (For instance, a c4 melodic note and a collapsed c major chord (c2 + e2 + f2) would both be at 12 o'clock.)


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