Hi Ian.
Both the Korg MicroArranger and Tyros 4 include line level input, so the vocal mic simply plugs into the VoiceLive Touch unit, of which incidently has 'phantom' power, which I need when using my AKG C3000 condenser mic. The vocal signal + efx processing + harmonies (generatied from the chords played on the kb sent to the VoiceLive via midi from the KB) are in turn sent out the VoiceLive's line-level output and enter the Yamaha T4 or Korg MicroArranger thru their respective 1/4" line level input jacks, with the final keyboard/vocal mix sent out the the respective keyboard's stereo output to the PA. - Scott