From the shepard tone to the perpetual melody auditory illusion

This paper discusses the use of the Shepard tone as a sound source in musical 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 it allows us to look differently at the instrument's range as well as at the phrasing in musical composition. Thus, this paper proposes a method of generating the Shepard tone relying upon an alternative spectral envelope, which as far as we know, has never been used before for the reproduction of the Shepard scale illusion. Using the proposed 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 titled "Perpetual Melody - contrasting moments", using exclusively the sound source as sound generator and the melody as musical content.