A nice person on Music Player Network (http://forums.musicplayer.com/ubbthreads.php/topics/2465083/20/This_Just_In_PX_5S) has spotted some manuals:

http://support.casio.com/manualfile.php?rgn=1&cid=008009154

I've had a scan .. I don't see that I can use any of the buttons to turn the layers on and off quickly but you can use the knobs or sliders to control volume. Also the phrase sequencer will play back smf0 midi files (which I didn't mention in my previous post because I figured this would be the case even though I haven't noticed that this was mentioned on any of the demos)(I reserve the right to be wrong here!)