Wendell Pierce is not a trombonist. He started taking lessons when he was cast as a trombonist, so his handling of the instrument would look credible on-screen. When Antoine Batiste plays, a professional trombone player off-screen provides the actual music. In season 4, a version of this behind-the-scenes story plays out in one of Antoine's story lines, when Antoine is hired to teach a non-trombonist actor (Lanny Fox, played by Wilson Bethel) to fake playing the trombone credibly during a movie shoot.