In July, news flew around the music world that the octogenarian Sir John Eliot Gardiner had struck a singer backstage after a performance of Les Troyens with Gardiner’s Orchestra Révolutionnaire et Romantique and Monteverdi Choir at the Festival Berlioz in remote La Côte-Saint-André. An assistant assumed the reins for the remaining dates of the very glittery Troyens tour, while a chastened Sir John took a time-out in his corner. Would he ever emerge? Yes, and with lightning speed! But not with his old orchestra. Gardiner’s instrument today is the newly founded period ensemble the Constellation Choir & Orchestra. For their debut European tour, Gardiner’s all-Baroque program sandwiches a Christmas mass by Charpentier between a pair of Bach cantatas. That’s exactly the program he had planned for this time with his previous associates. So there! —Matthew Gurewitsch