Choruses want to do Bach's B-Minor Mass the way that symphony orchestras want to do a Beethoven cycle, or opera companies want to do Wagner's Ring. The trick is not to actually get through it, but to render the seemingly endless details in the piece precisely and clearly while summoning the passion to do this powerful work justice. For the conclusion of its anniversary season, the S.F. Bach Choir will show us how it measures up to the Big One.