For Ann (rising) by James Tenney

Never, ever listen to / watch this while on drugs. Or your brain might kill you.

I haven’t read Doug Hofstadter’s latest book I Am A Strange Loop — but apparently one of the examples he gives of a stream / cycle / loop is: a sonic version of the optical-illusion-of-a-staircase-always-going-up-thing. It’s called a Shepard Tone and was invented in the 60’s.

Here’s what the Shepard tone looks like:

Here’s what it sounds like:

http://en.wikipedia.org/wiki/File:DescenteInfinie.ogg

Here’s the Editable Encyclopedia’s description:

The acoustical illusion can be constructed by creating a series of overlapping ascending or descending scales.

As a conceptual example of an ascending Shepard scale, the first tone could be an almost inaudible `C4` (middle `C`) and a loud `C5` (an octave higher). The next would be a slightly louder `C#4` and a slightly quieter `C#5`; the next would be a still louder `D4` and a still quieter `D5`. The two frequencies would be equally loud at the middle of the octave `F#`, and the eleventh tone would be a loud `B4` and an almost inaudible `B5` with the addition of an almost inaudible `B3`. The twelfth tone would then be the same as the first, and the cycle could continue indefinitely. (In other words, each tone consists of ten sine waves with frequencies separated by octaves; the intensity of each is a gaussian function of its separation in semitones from a peak frequency, which in the above example would be `B4`.)