The Chamber Orchestra of the South Bay...

The Chamber Orchestra of the South Bay this weekend will feature Ron Leonard, principal cellist of the Los Angeles Philharmonic--and an unusual change of roles by Frances Steiner, the chamber orchestra’s conductor.

At the Torrance Cultural Arts Center on Saturday and at the Norris Theatre in Rolling Hills Estates on Sunday, Steiner will put down the baton to join Leonard as co-cellist in a performance of Vivaldi’s Concerto for Two Celli.

Then Steiner will resume conducting, leading the orchestra in Boccherini’s Cello Concerto in B Flat Major, with Leonard as soloist. After intermission, the orchestra will perform Mendelssohn’s String Symphony No. 9.

The orchestra’s president and program annotator, Robert Miller, will give preview talks at 7:15 p.m. before the Saturday and Sunday performances.

What: Chamber Orchestra of the South Bay

When and Where: 8 p.m. Saturday at the Torrance Cultural Arts Center, 3330 Civic Center Drive, Torrance (310) 781-7171; 8 p.m. Sunday at the Norris Theatre, at Indian Peak Road and Crossfield Drive, Rolling Hills Estates (310) 544-0403.

Tickets: $20 ($15 for seniors and $10 for students.)