Members of the American Guild of Musical Artists and the American Federation of Musicians, two of the unions embroiled in contract negotiations with Metropolitan Opera management, rally this morning at Dante Park across from Lincoln Center. Jeff Lunden/for NPR hide caption

itoggle caption Jeff Lunden/for NPR

Austrian pianist Paul Wittgenstein (who later became an American citizen) lost an arm in World War I. He commissioned composers including Maurice Ravel to write pieces for the left hand alone. Bettmann/CORBIS hide caption

itoggle caption Bettmann/CORBIS