Someone walking through the factory, following a single piano as it takes shape, could forget a basic fact: Every Steinway is made the same way, from the same materials, by the same workers. Yet every Steinway ends up being different from every other--not in appearance, perhaps, but in ways that are not easily put into words: colorations of sound, nuances of strength or delicacy, what many pianists call--here's that word again--personality. Some Steinways end up sounding small and mellow, which is fine for chamber music. Some are so big and muscular and percussive that a full-strength orchestra cannot drown them out. On some, the keys move with little effort. On others, the pianist's hands and arms get a workout.