Bright colours, new hopes, and endless horizons. If you could set the American Dream to music, it鈥檇 probably sound very like Aaron Copland鈥檚 Appalachian Spring 鈥� the 1944 frontier ballet that took the old hymn 鈥楾is The Gift to Be Simple and sent it out into the world. It鈥檚 the calm, strong centre to John Wilson鈥檚 exploration of American music in the 20th century 鈥� a concert that ranges from the jazz age sheen of Barber鈥檚 comedy overture to Leonard Bernstein鈥檚 deliciously sophisticated take on Plato, in the form of a violin concerto. And to finish, a leading candidate for the title of the definitive Great American Symphony: Roy Harris鈥檚 taut, muscular Third.