This spring, both also paid gentle homage to their youth -- Allen with his first stand-up comedy routine in decades, with his brief appearance at the Oscars, Costello with his first straight rock album in seven years, the beguilingly titled When I Was Cruel. But like Allen's one-liners, Costello's return to noirish, "Watching the Detectives"-style guitar and garagey, "This Year's Girl"-style organ is just a surface trick. Beneath these flourishes, his melodies are as subtle, his lyrics as abstruse, and his arrangements as complex as any of those on his "mature" albums. For CD buyers, this might be a disappointment. For concertgoers, however, it promises a revue in which every aspect of his career will be informed by every other. If you didn't want Allen to leave the stage during that Oscar performance, imagine the pleasure in store during Costello's full-length look back.