Hallelujah! You know the chorus, but there is a universe to discover beyond those famous four minutes. This December, early-music master Richard Egarr makes his NSO debut conducting Handels Messiah, the iconic holiday favorite that can be hushed, roaring, and wondrously divine. However you know Messiah?as a yearly tradition, a piece you sang yourself, or music you have never heard live?there is nothing like being in the room when the first notes begin.