Assembled and composed for Leipzig's Christmas season, Bach's "Christmas Oratorio" is a celebration of the nativity of Jesus Christ originally performed over the course of six days beginning on Christmas Day 1734. As was often Bach's practice, he re-used music from several earlier works, including the independent secular cantatas nos. 214-216. In addition to chorus, the work features soprano, mezzo-soprano, tenor, and baritone soloists, as well as an orchestra configured differently for each of the six sections. The BSO hasn't performed this important work since Charles Munch conducted it in 1960. For these performances, Andris Nelsons and the orchestra are joined by an outstanding group of soloists and the Tanglewood Festival Chorus.