Shepard tone, named after Roger Shepard is a sound consisting of a superposition of sine waves separated by octaves. When played with the bass pitch of the tone moving upwards or downwards, it is referred to as the Shepard scale. This creates the auditory illusion of a tone that seems to continually ascend or descend in pitch, yet which ultimately gets no higher or lower.

Superposition-Superposition is the ability of a quantum system to be in multiple states at the same time until it is measured.

Sine waves-A sine wave or sinusoidal wave is the most natural representation of how many things in nature change state. A sine wave shows how the amplitude of a variable changes with time.

octaves- an interval whose higher note has a sound-wave frequency of vibration twice that of its lower note.

pitch-Pitch is a perceptual property of sounds that allows their ordering on a frequency-related scale, or more commonly, pitch is the quality that makes it possible to judge sounds as “higher” and “lower” in the sense associated with musical melodies.

auditory illusion- are false perceptions of a real sound or outside stimulus. These false perceptions are the equivalent of an optical illusion: the listener hears either sounds which are not present in the stimulus, or sounds that should not be possible given the circumstance on how they were created.

quantum system– a theoretical or actual system based on quantum physics, as a supercomputer.