Tuesday, March 25, 2008

Retro Loop

As I hinted in the previous post, seeing the Princess Bride DVD cover got my mind looping on loops again. I started thinking about Bach's crab canon from The Musical Offering, a 2-part canon in which the second part is the exact reverse of the first part. It occurred to me that if recorded with the right kind of synthesized timbre (specifiably, one without a distinct attack at the beginning of each note), it should be possible simply to play the audio backwards and have it sound the same. The result is quite effective. Here you can hear the canon played forwards. Actually, I only had my synth record the top part; then, I reversed that audio and layered it on to the original. The top, forward-moving voice is on the left channel and the reversed version is on the right channel. If you'd like to hear what happens when the audio is played backwards, here you go. It's pretty much exactly the same except the voices have switched channels. (Sorry, no hidden messages from the beyond.)

As with my Shepard Tone recording of Bach's spiral canon, I thought a follow-the-bouncing-ball score would make a nice visual accompaniment. It's not really all that easy to perceive the canonic effect unless one has listened often, so it helps to watch the music go in both directions. This video plays through the canon twice, the second time reversed, although YouTube doesn't preserve the stereo effect. Although I chose to display the parts on two staves, what you should try to do is just follow the top staff from both directions. The lightly shaded bottom staff is just there to show what the backwards voice is doing.

UPDATE: If you're wondering what a more conventional recording of this work might sound like backwards, you can hear it played forwards on the piano and then backmasked in this unusual little palindrome movie. Obviously, the sharp piano attacks create an odd whooshy effect when reversed.

UPDATE #2: For more than ten years (!), there have been two wrong notes in that video animation which has turned out to be one of my most viewed videos with over 180,000 views. I've finally created a new version with those notes corrected. Thank you to many YouTube commenters who've been reminding me of this error often!

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