You thought right.

I would also like to recommend a (?)recent(2011) paper investigating perpetual accelerando rhythms (no affiliation).

(note to myself -- too many brackets)

D. Stowell, Scheduling and composing with Risset eternal accelerando rhythms http://c4dm.eecs.qmul.ac.uk/papers/2011/Stowell2011icmc.pdf

In both, the illusion can be broken by focusing on the top or the bottom. This is pretty easy for me with discrete scales, but a bit harder in the glissando at the bottom of the article. I've got nothing on the perpetual melody, though.

that's exactly right. psychophysics is fascinating!

my favorite example of a shepard tone appears in an old wilco track that appears to be missing from the list.

notably shepard wrapping forms the basis of octave invariant chroma scales used in handcrafted features for old school automatic music transcription algorithms. (probably supplanted by nn stuff today)