7/13: Is the box office performing under par? Turn to Tchaikovsky, the "poet of cheerful melancholy" (as his countryman Nicolas Slonimsky memorably put it) for a quick fix. At least that's the old thinking. Does the formula still hold? Look around the borrowed Ted Mann Concert Hall at the Minnesota Orchestra's all-Tchaikovsky Sommerfest program and draw your own conclusions. Conductor Andrew Litton, beginning his 10th season as the festival's artistic director, is joined by Britain's Danny Driver in the First Piano Concerto, which, with no pretense of novelty, is preceded by the "Capriccio Italien" and followed by the "Pathétique" Symphony. (8 p. m. Fri. $25-$65. Ted Mann Concert Hall, University of Minnesota, 2128 S. 4th St., Mpls. 612-371-5656 or