The list of conductors who have hailed the Philadelphia Boys Choir and Chorale is a continuosly growing list: Wolfgang Sawallisch, Ricardo Muti, Eugene Ormandy, Zubin Mehta, Dennis Russell Davies and Charles Dutoit — among others. With a standard schedule of about 40 concerts in the Delaware Valley, performances with the Opera Company of Philadelphia, and the occasional trip abroad, the choir is well-known and well-loved. (You might have seen them in the Pennsylvania Ballet’s annual Nutcracker production without even realizing that’s who was delighting you.)