From the Shepard Tone to the Perpetual Melody Auditory Illusion
This work discusses the use of Shepard Tone (ST) as sound source in music composition. This tone has two musical interests. First, it underlines the difference between the tone height and the tone chroma, opening new possibilities in sound generation and musical perception. And second, considering the fact that it is (in a paradoxical way) locally directional while still globally stable and circumscribed allows us to look differently at the instrument's range and the phrasing in musical composition. Thus, this work proposes a method of generating ST relying upon an alternative spectral envelope based on the 40 Phon equal-loudness curve of Fletcher & Munson (1933), which as far as we know, has never been used before for the reproduction of the Shepard scale illusion. Using the proposed digital sound source, it was possible to successfully reproduce the Shepard scale illusion, even when applied to a melody. The melody was called "Perpetual Melody Auditory Illusion" because when it is heard it creates the auditory illusion that it never ends, as is the case with the Shepard scale illusion. Moreover, we composed a music, “Perpetual Melody – contrasting moments”, exclusively using the sound source as sound generator and the melody as musical content.
Article Published in the Proceedings of the 9th Sound and Music Computing Conference (SMC), University of Aalborg Copenhagen, Copenhagen – Denmark, July 2012 (pdf)
SMC oral presentation video at http://youtu.be/fVUQbOhu4ds
Musical exercises:
Pure data application (patch)
Original Shepard scale illusion (audio)
Reproduction of the Shepard scale illusion (audio)
Perpetual Melody Auditory Illusion (audio)
Digital Musical Composition:
Perpetual Melody - contrasting moments (patch) or audiovisual file at http://youtu.be/oLxki2sS7E0