I've seen Bosendorfer Imperial grands in the big halls in Europe that have a full octave extension in the left hand. Ninety six keys! I recently worked a college auditorium in Maryland that had a brand new Bosendorfer that only had what looked like a half octave extension.
The full octave extension does not have a melodic tone center to the notes, not to my ears at least, they seem to be there to add demension to chords in the left hand. But the notes sound beautiful, man those pianos speak.
The black and white keys are reversed on the extended part of the keyboard, the whole step keys are black, and the half step keys are white.
