Anyway, there is a single work on the program, the Missa Solemnis by Beethoven. Kurt Masur was to have conducted, but after three rehearsals, he realized that he was not physically capable of cubducting the whole thing in live performance. So he bowed out, and John Oliver, the conductor of the Tanglewood Festival Chorus stepped in.
As usual, here's something from the orchestra's website, with links available there for notes and discussion.
Beethoven's Missa Solemnis is one of the most significant works by one of the greatest of all composers. This monolithic late work stands with the Ninth Symphony, the late string quartets, and the late piano sonatas as the culmination of Beethoven's transformation of music. Beethoven intended the Missa Solemnis celebration of the election of his patron Archduke Rudolph as Archbishop of Olmütz in 1820, but didn't complete it until 1822.
At the Thursday performance, I wasn't overly impressed. There were some good moments (notably the violin solo during the "Benedictus"), and none that I thought were actually bad, but overall, and especially in retrospect, nothing really grabbed me, and the performance as a whole was not inspiring and exalting, as I had expected and hoped it would be. The Globe reviewer liked it better. I should add that listening to the broadcast during dinner this evening, I found it more impressive. It seemed livelier somehow.