Thomas Hampson has a sexy baritone that can sound rakishly charming (singing the role of Don Giovanni) or touchingly heroic (as Apollo). Porbably the most strikingly talented American male singer to have emerged since Sherrill Milnes, the Indiana native pairs up with soprano Edit Wiens to sing Brahms's German Requiem in the Chicago Symphony Orchestra season opener. A vast work built around texts from the German Bible, this unorthodox Protestant requiem commemorating the deaths of the composer's mother and soulmate Schumann is fervidly reverential and sentimental. Expect noble earnestness from Hampson and Wiens and glossy playing from the orchestra under the direction of Daniel Barenboim. The chorus, prepared by the semiretired Margaret Hillis, ought to shine as well. Friday and Saturday, 8 PM, Tuesday, 7:30 PM, Orchestra Hall, 220 S. Michigan; 435-6666.