Page  00000323 {TranSpell} Kazuaki Shiota College-Conservatory of Music, University of Cincinnati shiotak@email.uc.edu Abstract {TranSpell} is a software instrument created with Max/MSP. The synthesis algorithm relies on extraction of overtones from two fundamentals. Up to seventeen harmonics are independently panned across the stereo field. The graphical user interface allows control over overtone intensities, panning, tuning, and resonance parameters. Also {TranSpell} allows for performance of stored parameter changes and text control. 1 Introduction Having developed a composition system based on the acoustical properties of natural sound, overtone extraction, {TranSpell} was created to implement this algorithm. A compositional system for pitch and timbre was desired that would reflect the acoustical properties of natural sound, not the artificial pitch collections generated by serial techniques or other algorithms. In the overtone extraction theory that is applied in {TranSpell}, the timbral pivot tones create a smooth transition between the two different overtones. 2 Overtone Extraction Theory The overtone extraction theory describes pitch/timbre generation by means of extracting paired notes from the harmonic series above two fundamentals. Pitches that appear in both overtone series are chosen. Just tuned pitches within 50 cents of each other are considered the same pitch. The overtone extraction theory will be described more completely in a future paper. 3 Timbral Pivot Tones Although the gap between the paired notes is up to 50 cents, both notes are close enough to be heard as the same pitch. Because the pitch is heard in both series, it can be heard as a pivot tone between the two series. The extracted paired notes are preserved even when the fundamental is changed from one to another. Consequently, the two sets of the extracted overtones can mutate mutually based on the other fundamental and to preserve the analogous timbre through the pivot tones. That is the concept of the timbral pivot tones and it enables to create a smooth transition. 4 {TranSpell} {TranSpell} is implemented in Max/MSP patches to allow performance by a musician. The synthesis algorithm is based on resonant filtering of a source sound (white or pink noise, or microphone input) is filtered by a resonant filter to produce the common overtones of two selected fundamentals. All the notes are displayed graphically with the cents modification. 5 How musician interacts The musician can sculpt ranges and rates of change in volumes, panning and resonance formants of the overtones. Stored parameters can be triggered by keyboard events, and parametric changes can be executed by text commands. Tuning of overtones also can be modified graphically. The main window is in figure 1. f12 n+fd2+ over(l) 0 4-0- - 0------0-0------- ---0-0---- ------------- Figure 1. Overtones are notated in the conventional staff paper with the cents modification to realize the harmonic overtones from the equal temperament. 6 Compositions and Performances In "The Signals from the Starlight," commissioned by the Next Ens, {TranSpell} was successfully used as a musical instrument. Also {TranSpell} was implemented to the film, "the circulation of memory" which has been selected by the SEAMUS conference 2006. In conclusion, {TranSpell} is a software musical instrument in which timbre is manipulated according to overtone extraction, panning and tuning, using pivot tones to transform timbre. 323