"The way it looks is you plug your mic into the vocal processor, then plug the output of the vocal processor into the keyboard's Mic/Line-In--that's all there is to it."

Then how does the device know what key to create harmonies in? You must have to plug a midi out of the keyboard into the midi in of the vocal processor. Anything else?

I asked what cables are needed. I would imagine you need a power cable - or does the device work on batteries? You need an extra mic cable. I would imagine you need at least one midi cable. Anything else?

Beakybird