The end-of-the-year holiday season is make-or-break time for many performing arts groups, and in large cities like Philadelphia, where dozens of groups are competing for audience, getting a big enough slice of the ticket revenue pie becomes crucial, and difficult. “In the last three years, the Philadelphia Orchestra has added eight holiday concerts, supplementing its traditional two performances of Handel’s Messiah and its yearly New Year’s Eve concert. The Philly Pops, which in 2000 gave its first holiday-themed concert, now offers six. The Kimmel Center itself also has added holiday shows such as the Vienna Boys Choir. Smaller arts groups also are relying ever more heavily on holiday receipts.”