Risset's Endless Glissando

Sound files are AIFF and animations are quicktime. Be sure you have the appropriate player/viewer software to hear and see these.

Shepard Tones (The Linear Movies)

Here are pair of quicktime movies showing how the partials cycle. Your WWW client will need to support the viewing of Quicktime movies.

In these two the frequency is linear on the x-axis. Each partial is one octave higher that the one previous, so the frequency of any partial is 2 times the one previous. With the partials all displayed the same color and the animation set to loop, the endless illusion can be easily seen. Displayng the partials in different colors it is easier to see what is really going on.

Shepard Tones (The Logarithmic Movies)

Here the pair of quicktime movies show the partials logarithmically on the x-axis. The partials now appear equidistant from each other. Again with the partials all displayed the same color and the animation set to loop, the endless illusion can be easily seen. Displayng the partials in different colors it is easier to see what is really going on.

Csound .orc and .sco files

Here you can see this instrument implemented in Csound. The .orc file uses 10 sin oscillators. The .sco file cycles the partials at different rates. A bell-shaped curve is used to control the amplitude envelopes of the instrument's partials. It is stored as a table that is calculated by the Bellfunc instrument and score files.

Hearing the endless glissando

Here are a couple of sound examples of the endless glissando. You might prefer to load them to your local hard drive before playback. These files are in both 16-bit AIFF format and MOV (Quicktime, audio only), so the appropriate player will be needed. The first example (920K AIFF// MOV) is the sound file calculated from the Csound .orc and .sco files above. The second example (685K AIFF// MOV was created by modifying some of the score parameters. Can you guess how it was done? The .sco file for this sound file is here.