Chicago Symphony Orchestra, James Levine, piano and conductor, Deutsche Grammophon 431 625-2 (one CD), $16.98 . CODE: BAT-12

Chicago Symphony Orchestra, James Levine, conductor, Deutsche Grammophon 431 698-2 (one CD), $16.98 . CODE: BAT-13

Here are new discs by a top American orchestra and a top American conductor, recorded in top modern sound, of twentieth-century classics from two different American universes. The Gershwin disc features a stunning Rhapsody in Blue in the rarely heard but very snappy original version for jazz band as well as a first-rank performance of another of Gershwin’s most popular big works, An American in Paris . The other disc contains “difficult” modern masterpieces from the 1950s and 1960s. The authoritative performances of works by Schuller, Babbitt (for orchestra and synthesized tape), and Cage (based on chance) may not win many new converts, but the main attraction, Elliott Carter’s twenty-three-minute Variations for Orchestra , from 1954, should. Carter, who is now eighty-five and who as a boy was encouraged to compose by Charles Ives, may very well be remembered as America’s greatest composer of his time, and this disc gives a good indication why. The music is atonal, complex, and uncompromisingly experimental; it is also viscerally powerful, shapely, immediately grasped, and lovely in multitudinous ways. If you want to understand and truly enjoy what American modern classical music was all about when it seemed most forbidding, there is no better place to start.