James Levine, who has been conducting an elegant account of Mozart's "Le Nozze di Figaro" at the Metropolitan Opera, brings the Met Orchestra to Carnegie Hall for its first program of the season. The eminent pianist Maurizio Pollini is the soloist in Mozart's beloved Piano Concerto No. 21 in C. Then Mr. Levine, acclaimed for his Mahler, will lead his players in the composer's powerful Ninth Symphony.