H & H's page about Messiah has further links and introduces the performance as follows:
A tradition for 159 years—make it yours! Harry Christophers conducts the Period Instrument Orchestra, Chorus, and internationally acclaimed soloists in Handel’s dramatic masterwork. Don’t miss Canadian superstars soprano Karina Gauvin and countertenor Daniel Taylor, British tenor extraordinaire James Gilchrist, and Boston's own premier baritone Sumner Thompson in this season’s unique rendition of this Boston tradition. No holiday season is complete without Handel’s stunning oratorio.