Hi Again,
My mistake It was not a cd rewriter as I had assumed it was some thing they call CD remix play. It was on the SX-MB100 and rather than me explain it (and get it wrong again!!) this is what Technics say it does..

Unleash your creativity with CD Remix Play!
Have you ever imagined that you're part of the band playing the music on your favorite CD's? Dream no more. The MB100 automatically detects* the tempo of a song while a CD is playing and lets you use the four central performance pads to remix phrases. You can add Voice, Scratch and other sounds in time with the beat by pressing the pads or keys, and mix sounds into the rhythm section. You can remix the rhythm too, with the help of the Fill-In button. You can also play along in unison, adding different sounds and mixing musical phrases.


Don't think I would ever use a feature like this but others may find it useful. I had the Roland EM2000 once over and some people raved over the 'D-beam' controller. I never did find a practical use for it. For me the above would be just the same I suspect. Apologies if I had anyone rushing to buy a Panasonic k/b for the cd rewriter !!!
ttfn
Tony