Shepard-tone ambiguity arises in real music such as Bach’s organ works

Evidence

The pedal line consists of a sequence of five descending scales with eight notes in each except the last. Each scale ends with an upward leap of a minor seventh, and the exact moment at which the upward leap occurs is often perceived with some ambiguity, even when listeners have the score in front of them. The strength of this effect depends on the particular stops used. This ambiguity is particularly common among listeners in the third bar of the extract, where the upward leap is often very strongly perceived as occurring one or even two notes later. This could be due to the entry of a new part in the left hand playing F3, which starts as the pedal part jumps up to written B♭3. — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 1645

Categorization

• SHARE: An organist would love knowing Bach’s BWV 542 pedal line triggers Shepard ambiguity — send to any musician friend.
• XREF: Connects Shepard tones discussed earlier in the chapter to actual repertoire, echoing the Fantasia example.