By Caldwell Titcomb. October 2: The Longwood Symphony Orchestra opens its 28th season, the sixth under conductor Jonathan McPhee, with a program of Sibelius and Delius. Award-winning Zina Schiff will be soloist in the demanding Sibelius Violin Concerto. Also on the program are Sibelius’s “Karelia Suite” and Delius’ lovely “Walk to the Paradise Garden.” At…