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Uploaded on Mar 2, 2008
Canon a 2 per Tonus, from Bach's "Musical Offering." The top voice plays a version of the tune given to Bach by Frederick the Great. The other two voices are in 2-part canon, with the bottom voice leading and the middle voice following a measure later and a fifth above. The canon is designed so that it modulates up a whole step each time through; thus, after six times through, the music returns to C Minor where it began, but an octave higher.
This recording, inspired by a suggestion in Douglas Hofstadter's "Gödel, Escher, Bach," uses the Shepard Tone technique, meaning that a lower octave is constantly being faded in for each voice while the upper octaves slowly fade. Thus, by the time C Minor is reached again, the lower octave has taken over; so we're back exactly where we started.
The bottom part (leader) is recorded on the left channel, and the middle part (follower) is recorded on the right channel to make it easier to follow. [UPDATE: The stereo effect didn't transfer to YouTube. However, the stereo separation does work on the downloadable versions that you can access at the link below.]