Shepard Tone

Shepard Tone: A Shepard tone, named after Roger Shepard, is a sound consisting of a superposition of sine waves separated by octaves. When played it creates the auditory illusion of a tone that continually ascends or descends in pitch, yet which ultimately seems to get no higher or lower. (wiki)

Recent example the end of Wilco's "Born to Die"

Wilco shepard tone

or The Beatles "I am the Walrus"

Walrus Shepard Tone

Historical example would be JS Bach "Never ending Canon"

Bach Shepard Tone

The Shepard tone supposedly elicits a similar response to most folks who listen to it, that it is foreboding, possibly depressing, even scary.