Two superstars will be playing two No. 2 concertos too difficult for most other mortals. You’ll have to watch them on two different days, but you get to hear Rachmaninov’s tuneful Symphony No. 2 twice. Yuja Wang does Prokofiev’s Piano Concerto No. 2 on October 31; then Lang Lang comes on board to perform the Prokofiev Concerto No. 3 on November 1-2.