William Grant Still wrote his Symphony No. 2, Song of a New Race, for the Philadelphia Orchestra to premiere in 1937, conducted by Leopold Stokowski. On Jan. 16-18, that same orchestra will play it again, this time under the direction of Yannick Nézet-Séguin, who will also conduct Margaret Bonds’ The Montgomery Variations and Tchaikovsky’s Piano Concerto No. 1, with soloist Yuja Wang.