Unlike most chorus pedals, the Empress has a (voice) knob to adjust the delay time, allowing, says New Zealand-based manufacturer Red Witch, "an infinite number of analogue chorus pedals in one box".
Modulation depth and speed (velocity knob) are adjustable, as is the wet/dry blend via the mix control. You can choose between vibrato and chorus modes, with the former yielding vintage vibe sounds, plus a neat line in rotary speakers, but it's the chorus that's special - sparkly, spacious and varied.
Early Boss units are the benchmarks here, and next to vintage CE-1 and CE-2 units the Empress lacks some of their warmth, with more of a 'modern' treble content, but is able to replicate the range of chorus available and then some.
It's especially good when hooked up in stereo - like mic'ing a JC-120's speakers separately and panning them. No wonder Andy Summers uses one. Great sound and versatility make this one of the best chorus pedals around.