At some point, the crossover genre was bound to get to the heart of the question: What makes classical music classical? Joe Jackson's jazz- and pop-influenced Symphony No. 1 argues that's all in the structure. The idea is far from new: Ellington composed tone poems for his jazz band, Glenn Branca has written full symphonies for electric guitars, Mikel Rouse has structured entire operas from house music and hip-hop. Those who wince at the idea of a "pop" symphony on principle need to get out more. The combination of a major artist with a major label, though, raises the ante. Unlike Jackson's earlier HEAVEN AND HELL -- essentially a thematic pop album with a larger string section -- the Symphony No.1 actually fuses the composer's recognizably eclectic style to an entirely different format. The ten-member band combines a jazzy freedom of the moment with a clear, classical sense of direction. For fans who've wondered where Jackson's been hiding recently, this Symphony shows he's still very much around. His ideas just don't fit the four-minute format anymore.