When conductor Semyon Bychkov fell ill halfway through an afternoon rehearsal, assistant conductor Joshua Gersen stepped in – and then got to lead the orchestra at that night’s performance as well, “leading impassioned and incisive accounts of Tchaikovsky’s symphonic poem ‘Francesca da Rimini,’ a piece he had never conducted, and the intense ‘Pathétique’ Symphony, a work he had previously led only in part.”