"She," actually. And yes, they asked for jazz-influenced tracks since the game seems to be going for an old-timey cartoony American vibe (in spite of the anime-style graphics), which is a departure for her. She says she's always wanted to write jazz though, so hey.
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[NO BARKLEY NO PEACE] Ace Detective in Sir Charles's Police
http://www.youtube.com/watch?v=kkOj5DAJu2A