Octave Illusion

This is a realization of Deutsch’s Octave Illusion created in VCV Rack with 2 sine wave oscillators as described in http://deutsch.ucsd.edu/pdf/HRT_OctIll_Ch_1981.pdf

The pitch is modulated up with a square wave. One oscillator is set for 400 Hz and the other for 800 Hz. When the square wave goes high, Oscillator-1 goes up an octave and Oscillator-2 goes down an octave.

Change the tempo with the frequency of the square wave (LFO). An LFO frequency of 2Hz results in a switching of 250ms (same as the original 1974 setup).

Note that the oscillator frequency switching occurs whenever the LFO changes (and it is synchronous between the left and right channels). This is different from, say, the CSound method (which switches at the zero crossing) or the CMusic method (which uses “Splice” to switch at the lowest or greatest slope).

I’m using the CLK just to reset the sync on the VCOs. This is useful in more complex patches where we use a sequencer and need the VCOs to be in sync.

More information on the Octave Illusion can be found here:

http://deutsch.ucsd.edu/octave_illusion
https://en.wikipedia.org/wiki/Octave_illusion

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    • Category: Other
    • Revision: 1.0
    • License: Academic Free License v3.0
    • Modified: 4 years ago
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