Friday: Sommerfest's second weekend juxtaposes large and small. For early risers, there's an enticing chamber program, the last of this year's festival, offering seldom-heard works by Americans Charles Martin Loeffler and John Corigliano, and topped by Mozart's incomparable Clarinet Quintet, with Osmo Vänskä as clarinetist. And when evening comes, there's the unabridged Minnesota Orchestra, under Andrew Litton's baton, in music by two of Russia's three great composers for the dance: Tchaikovsky ("Nutcracker," generally confined to the holiday season) and Prokofiev ("Romeo and Juliet"). Only Stravinsky is missing. (Chamber music: 11 a.m. Fri. $20; kids $12. Ballet: 8 p.m. Fri. $18-$48. Orchestra Hall, 1111 Nicollet Mall, Mpls. 612-371-5656 or minnesotaorchestra.org.) LARRY FUCHSBERG