The MM-979 Quad Quantizer is, as it's name implies, a quantizer with 4 ins/outs allowing you to independently quantize 4 signals.

Select from 5 Custom slots (CV-controllable), select your intervals on the 'keyboard' on the right, then you can pick your root note with the ROOT control (also CV-controllable!).

The ROOT cv-control goes off the 1v/oct pitch of the incoming CV signal. So send it a C note (or a nice round number of volts (1.0v, 2.0v etc.)), and you'll get a C. Send it a G Note (0.58v, 1.58 etc..) you'll get a G, etc.. Great if you want to route an external sequencer into the ROOT input so change keys easily.