Friday at 7:30 p.m., they'll re-create one that Handel conducted in London that added a few arias to feature some of his favorite soloists from the chorus. Since the Philadelphia Singers have always featured ensemble members as soloists, this version becomes a perfect display piece for Korn's 30-voice ensemble. Tickets: $9 to $35. Info: 732-3370.
Another choral organization, the Music Group of Philadelphia, has chosen more offbeat repertory. They'll sing Respighi's ravishing cantata "Laud to the Nativity" and Schoenberg's rarely-heard setting of a nativity poem ''Friede auf Erden" ("Peace on Earth"). The concerts, tonight at 8 at the Church of St. Luke and the Epiphany, 330 S. 13th St. and Sunday at 8, Church of the Redeemer, Pennswood and Fishers Roads in Bryn Mawr, will be conducted by Sean Deibler. Tickets: $12. Info: 482-9905.
Finnish composer Jan Sibelius knew the Philadelphia Orchestra and Eugene Ormandy well. His Seventh Symphony was given its world premiere by the orchestra in 1924, and we'll hear the work again at the Academy of Music Friday at 2 plus Saturday, Monday, and Tuesday at 8.
Dutch conductor Hans Vonk returns again as guest, also leading Beethoven's monumental Third Symphony, the "Eroica." Another morsel of Sibelius opens the program, the famous "Swan of Tuonela." This work has a haunting, mystical quality always ideally captured by Louis Rosenblatt's ravishing English horn solo. Tickets: $10 to $60. Info: 893-1999.
Opera North's cancelled spring performance of Donizetti's "Don Pasquale" has been rescheduled for tomorrow night at the Keswick Theatre in Glenside at 8. Tickets: $15 to $25. Info: 472-3111.