Hi Brian

I use a headphone splitter cable (3.5mm) plugged into the aux input on the VLT.

Feed the headphone output from the keyboard into one socket of the splitter cable to trigger the harmony. Take the feed from the other splitter socket to one of your inputs on a mixer or your audio input. The output from the VLT goes into your other audio input.

In the menu system on the VLT you can reduce the volume of the aux output to zero so that only the vocals are sent to the output.

You then have the keyboard on one input and the vocals on the other. The feed from the keyboard to the VLT is only used to trigger the harmonys.

Hope this helps.

Regards

Col