Vivaldi's Magnificat probably dates from shortly after the 1726 death of composer C.P. Grua, which resulted in his having to provide sacred music for the Venetian orphanage and convent he enjoyed a long-standing relation with: the Ospedale della Pieta. There are actually three versions of the work: 1) for single chorus and orchestra (RV 610); 2) for double chorus and two orchestras (RV 610a); and the final version (RV 611), which takes six movements from replaces the other three movements woth solos written for specific singers at the Pieta: Apollonia, la Bolognesa, Chiaretta, Ambrosina and...