Generally, when contemporary performers have taken on retro projects like this one, they have tended to emphasize their fidelity to the sources -- consider Linda Ronstadt hiring arranger/conductor Nelson Riddle to recreate his string backgrounds for albums like What's New.
Chicago takes a different approach to the swing band classics it tackles here -- it Chicago-izes them.
The arrangements are by trombonist James Pankow, who manages to make everything from Duke Ellington's "Caravan" to Glenn Miller's theme "Moonlight Serenade" sound like a lost Chicago track.
Those familiar with the originals, many of which were instrumental hits, may be surprised to hear the lyrics to songs like "Sing, Sing, Sing." Clearly, the group is aiming more at pleasing contemporary fans than evoking nostalgia, and it succeeds in reinventing some well-established standards, even if older fans may find some of these versions radically altered.