The Rozhdestvenskys are fast emerging as Russia's most prominent musical family. The father, Gennady, son of a well-known Moscovite maestro and singer, joined the Bolshoi Theatre as conductor in 1953 at age 22 and oversaw a number of important premieres. A skilled practitioner of politics and the recipient of the Lenin prize, he became, in the 80s, the first Soviet to hold a top post with an orchestra in the West. At home he was even permitted to form an ensemble of his own, the State Symphonic Kapelle, to record all the major Russian orchestral works. An avid chamber pianist, Gennady sometimes does recitals with his wife, pianist Viktoria Postnikova, and his young son, violinist Alexander Rozhdestvensky. During his two-week stay at Ravinia he will spend the bulk of his time conducting the Chicago Symphony and a parade of renowned soloists, including cellist Heinrich Schiff, pianist Emanuel Ax, and violinist Nadja Salerno-Sonnenberg. But he wisely set aside one evening to play with his family. Their chamber program is unusually thoughtful: the First Violin Sonata by the prolific Russian avant-gardist Alfred Schnitke and Six Pieces for Solo Piano by the American maverick Edward MacDowell, based on Heinrich Heine's poems. Thursday, 8 PM, Murray Theatre, Ravinia Festival, Green Bay and Lake Cook Rds., Highland Park; 728-4642.