Shepard Tone

(From Wikipedia) A Shepard tone, named after Roger Shepard, is a sound consisting of a superposition of sine waves separated by octaves. When played with the base pitch of the tone moving upward or downward, it is referred to as the Shepard scale. This creates the allusion of a tone that continually ascends or descends in pitch yet ultimately, seems to get no higher or lower. It has been described as a "sonic barber's pole". I hear this effect in scary/sci-fi movie sound tracks.

The Möbius Filter comes as native plug-in that works on either mono or stereo sources. It has an X/Y pad with a virtual joystick you can click and drag around to set the center frequency at 175Hz to 10.8kHz on the X-axis and the resonance of the filter expressed as 0 to 100 on the Y-axis. Higher resonance values cause the filter to nearly whistle.

There are two filter types: "phaker" and peak and you can pick in which direction the Shepard tone filter goes, up or down. I liked the host sync (with selectable sub-divisions) feature to lock the sweeps to the song tempo--it makes this crazy effect sink more into the track. You can also let it free-run with its own LFO and there is a Wet/Dry fader and a stereo control for widening the stereo field of the filters.

The Möbius Filter has pop up help windows explaining each control and all controls are automatable including resetting the joystick to center position. You can also automate the Pause button to freeze the filter frequency at any point in the up or down sweep for a static effect.

I especially liked automating the direction of the sweep for certain moments in the song and automating the Joystick by adding both Frequency and Resonance to the automation list. I liked using the iZotope Möbius Filter to randomize reverb returns and delays and I used it as a much more interesting phaser or flanger psychedelic effect.

Möbius Filter is available now for $49 MSRP and for more information and download, check: www.izotope.com/mobiusfilter.