Need proof that Apollo's Fire has grown? Attend its new production of Monteverdi's "L'Orfeo." Seventeen years after their last performance of the 17th-century masterpiece, the Baroque orchestra and director Jeannette Sorrell are reviving the work, this time in a semi-staged production with a cast of experts.

"It feels like a reunion with an old friend," Sorrell said, after the start of rehearsals. "I feel like this production is a once-in-a-decade kind of thing for us." Indeed, "Orfeo" has emerged as a sort of barometer for Apollo's Fire. In 1996, when the still-young group first performed it, the opera convinced Sorrell she was on the right path, when crowds turned out in the aftermath of a damaging storm. The next time, in 2001, it went down as one of the group's early successes in recording.