Pitch deceptions

Shepard's scale

Here are two scales based on Shepard's scale.

Is the last note really an octave above the first one?

Major diatonic scale

Minor diatonic scale

These could be said to examples of musical strange loops. For more on music and strange loops see 

Gödel, Escher, Bach: an Eternal Golden Braid  

by Douglas R Hofstadter

Pitch dependency

Listen carefully to the following tone sample of a pure tone note A.

Now listen to this pure tone note E.

Now listen to both notes together - a perfect fifth.

Both tones can also be heard in the following sample, except that the A is intermittently faded out. The E is the highest of the two tones, and this note itself does not change. However, the perceived pitch of any note or sound is not an objective property of the note or sound itself. It depends on objective properties of the note or sound, but it also depends on subjective factors, including both the physiological condition of the ear, and the psychology of perception.   

For most people, the pitch of the E, even though the sound itself does not change, is affected by the activity in the other tone A. Each time the lower pitch A stops, the pitch of the E can be heard to drop a little.   

Pitch dependency sample