SKnote have announced Retoone which they describe as a simple, MIDI-controlled effect for pitch-shifting, doubling, choir, chorus. Here's how they describe it...
Pitch-shifting and three voices choir
Pitch-shifting: up to three independent voices are generated from the input. Each voice is shifted up to 1 octave up or down, with formant control. Frequencies can be controlled by midi notes. Pan control for each voice is available, with mid-side ratio control and "humanizing" parameters. Chorus: the additional voices can work in "chorus" mode (modulated periodic pitch shift) and can be placed on the stereo field with mid-side ratio control. Pricing and Availability: