Musicians and podcasters might find these links of interest (and I certainly plan to employ some of these tricks, now that I’ve discovered some open source toys):

• Three audio paradoxes: Shepard’s ascending tones, falling bells, and a “quickening” beat.
• Shepard’s pitch circularity in detail. (It’s worth noting that you can hear Shepard’s illusion at the beginning of Queen’s A Day at the Races album.)
• More audio illusions.
• The tritone paradox.
• The tritone paradox’s effect on linguistics.
• A list of demonstration CDs.