Eventide have long offered a plug-in version of their 1972 Instant Phaser hardware, and now they've revisited it to add both new capabilities and the ability to 'age' the circuity by introducing modelled component value drift.
StageOne is a plug-in designed to manipulate stereo imaging, by extracting a signal that corresponds to what we hear as the 'phantom centre' and processing this independently of the rest.