Listen • 1:00 / Have you ever wondered why pianists need page turners? They’re not, after all, the only ones who use both hands to play their instruments. The answer is that piano music goes by too fast: you can only fit half as much music on one page of piano music as you can on one page of music for a non-keyboard instrument. And that’s for the simple reason that in printed piano music, each line of music takes up two lines, one for the left hand one for the right. Each set of two lines together, for left hand and right, is called a “system.” And I should mention that in piano scores for