Working without a music director, this British period-instrument ensemble is famous for its collaborative, deliberate nature. The time they devote to rehearsal is always evident in their striking, clear performances, which often focus on the Baroque and Classical periods. (They stretch into some Romantics, too, with balanced takes on Mahler or Fauré.) Yet the group's intense energy is best communicated through works by Beethoven and Vivaldi as well as lesser-known composers like C.P.E. Bach (son of J.S.). Whether playing warhorses or rarities, their interpretations sparkle with invention.