Violinist Johnny Gandelsman, co-concertmaster of the extraordinarily popular and future-looking chamber orchestra The Knights, will make his Ravinia solo debut on the $10 BGH Classics series on Sunday,Sept. 1. His program will include Stravinsky’s Elégie, Philip Glass’s Strung Out and two of Bach’s works (one sonata and one partita) for unaccompanied violin. He returns to play with The Knights on Tuesday,Sept. 3, on a concert that features tenor Nicholas Phan, an alumnus of Ravinia’s Steans Music Institute. That program includes Copland’s Quiet City and, to mark the centennial of Benjamin Britten, his Serenade for Tenor, Horn and Strings. Gandelsman was here earlier this summer with the ensemble Brooklyn Rider.