Does anybody have any knowledge of dual-keyboard pianos? Years ago I was invited to give a performance of the Waldstein Sonata at a local Musical Society meeting, and when I was called up to the stage and opened the keyboard lid of their grand piano, I was horrified to discover two keybords staring at me! I'd never seen or even heard of such a thing, and got thoroughly lost in the performance because as I played one keyboard, my eyes kept looking at the one just above it - it was a most horrible experience from which it took me years to recover. Anyway, I was just recently looking at a documentary of Khachaturian (directed by Peter Rosen - wonderful, I thoroughly recommend it) when during one of the interviews I spotted a dual-keyboard grand piano monster lurking in the background - which brought back all my nightmares. Now I am wondering who made such instruments and what was the purpose for having dual keyboards, except to terrorize unsuspecting pianists?