Original Off-Broadway Cast, 2002 (Original Cast Records) (3 / 5) A musical about a math problem? It’s a crazy notion, but composer-lyricist Joshua Rosenblum and librettist-lyricist Joanne Sydney Lessner make it work. Their show was inspired by the controversial last theorem of French mathematician Pierre de Fermat, which has the mythical qualities needed to support a dramatic framework. Fermat’s Last Tango is a bizarre, surprisingly effective, mostly true musical detective story. The creators changes few of the real-life facts beyond renaming the central figure Daniel Keane. Femat himself appears, taunting and yet assisting Keane throughout the show; if the device seems a bit silly at first, it works because of the epic scope of the musical. (Euclid, Newton, Pythagoras, and other mathematicians also appear.) The score is often operatic in weight, and the talented cast is more than up to the challenge. Chris Thompson displays a booming baritone as Keane, Jonathan Rabb’s pompous Fermat is lots of fun, and the members of the ensemble (Christianne Tisdale, Carrie Wilshusen, Gilles Chiasson, and Mitchell Kantor) are excellent. Perhaps the best performance on the cast album comes from Edwardyne Cowan, who plays Keane’s wife. With her beautiful voice, Cowan puts over the show’s one concession to traditional musical comedy, a terrific number titled “Math Widow.” But there are several other enjoyable songs here. Although Fermat’s Last Tango is not recommended as light background music, it’s definitely worth a listen or two. — Matthew Murray