Mobius Filter from iZotope is a plug-in based on the Shepard Tone, which produces the illusion of an infinitely ascending or descending filter sweep. The effect can add motion to otherwise static material without obscuring the underlying frequency content of the source audio, create massive filter swells, mind altering alternatives to flange effects, or provide fresh inspiration for exploratory soundscapes.
Useful for any source material, the software can be set aggressively and then dialed back with the mix control to get a sense of complex motion while still preserving the integrity of a mix. Or liven up a dull vocal track without detracting from its intelligibility. A stereo slider control can widen the stereo field to any amount for enhancing sound effects and sound design, while a software XY pad can be used to draw in custom sweeps.