Dave

When I had the Pa600 and the Voice live Touch 2 I found the output from the headphone socket on the Pa600 into the aux input of the VLT worked really well no midi involved.

Perhaps that may solve your problem. On the older Korg keyboards Pa2x, Pa800, and the micro arranger you had to select the chord channel on the keyboard for the midi to work correctly but this did not function on the Pa600, maybe it's the same on the Pa900. I reported it to Korg but nothing changed.

Hope this helps

Col