As detailed in our text, auditory stream regulation is a psychological phenomena in which sounds of same timbre and pitch are grouped become perceptually grouped by the listener. Musicians have taken advantage of this phenomena so as to produce the perception of multiple melodies from one melodic line. Although I do not play any instruments, my father is a guitarist. He plays primarily thrash metal, I have always grown up hearing the melodies of his guitar throughout the house. I have always been impressed by his talent to create such intricate music, all by himself. After learning of auditory stream regulation and implied polyphony, I now have a better understanding of how my father can create such intricate and seemingly complicated pieces of music with only one guitar.
The video below demonstrates this phenomena, as a young man plays a piece by Baroque composer J.S. Bach.
The rapid repetition of the high and low notes, although all a part of the same melody, appear to be separate, independent melodies. The video also incorporates a middle set of notes that then appear to hold a third melody. The distinction of the two notes as a single melodic unit can be heard towards the end of the video, once he slows down the pace.