Oli Larkin has released The Endless Series, a set of three plugins based on the auditory illusion known as Circular Pitch (or more commonly the Shepard/Risset tone). Circular pitch means a sound that appears to be constantly ascending or descending but ultimately doesn't seem to get any higher or lower (it returns to where it started).

Endless Tone (released last month) can be used to generate classic Shepard/Risset tones. It also can be used as a ring modulator either with an internal (sine wave) carrier or using the audio input. Endless Tone is a free plugin.

Endless Flanger is like a traditional flanger except that instead of flanging up and then down, it appears to continuously flange in one direction.

Endless Phaser works in the same way but instead of using delay lines it uses filters to produce its effect.

The Endless Series costs £10 GBP. You can buy Spacestation (VST Doppler Effect) and The Endless Series as a bundle for £15 (a saving of £5 off the separate prices).

Demo versions are available.