Taken in the context of modern cultural offerings of singular musical artistic expression, Joni Mitchell’s 1969 masterpiece stands out as a touchstone of style, lyricism and theme. Roger Emerson, himself carving out a space in the late-’60s southern California rock scene when “Both Sides Now” was written, sets up the Canadian’s inimitable refrains and rhymes in a choral setting in a way that is absolutely astounding.