It sounds like another one-joke show: Florence Foster Jenkins, a wealthy woman who can't sing on key, is blissfully oblivious to both her lack of talent and to the reaction of those who hear her. If that was all there is to Diamond Head Theatre's production of “;Souvenir,”; the only question would be whether Stefanie Smart and director John Rampage could keep the premise fresh and funny for the duration of a full two-act play.

That they do, but “;Souvenir”; is much more than that.

Smart is superb at the formidable task of singing far enough off-key to jar the ears of even the most karaoke-tolerant members of the audience. She also brings to life a woman who's so supremely self-confident that when the key she was almost hitting didn't match her accompanist's piano, the obvious explanation—to her mind—was that “;the piano must be out of tune.”;

Smart's skill is underscored in a scene that features a recording culled from Jenkins' legendary album, “;The Glory (????) of the Human Voice.”;

  BUT “;SOUVENIR”; has two other things going for it. Playwright Stephen Temperly's brilliant script is one. Smart's co-star, Laurence Paxton, is the other. Paxton has been known for years as a stellar vocalist, but as Cosme McMoon, Jenkins' long-time pianist, he steps into a role that showcases him as an actor and pianist. To dub it a “;career best”; performance would be to slight his many successes in singing roles, but it is certainly an impressive career milestone.

Paxton is on stage for the entire show, sometimes as the narrator is recalling events of a generation before, and sometimes in flashbacks of McMoon and Jenkins' relationship. The latter shows the evolution of the duo's partnership, from their first meeting in 1932 through her performance for a sold-out house at Carnegie Hall in 1944.

At first, McMoon explains to the audience, he stuck with her because the money she paid him made it possible for him to pursue his own (unsuccessful) career as a songwriter. As the years pass, however, the pianist finds that he has developed feelings of protectiveness for the singer.

The audience has a similar experience.

Act I establishes Smart's ability to sing off-key and Paxton's appeal as an engaging narrator and comic actor.

Much of Act II re-creates Jenkins' 1944 sold-out show at Carnegie: More off-key singing, kitchy costumes, odd facial expressions and mangled pronunciation of lyrics in several languages. Sound Designer Mikel J. Humrickhouse gradually fills the theater with crowd noise, and when the “;audience”; starts to laugh—and, for the first time in her career, Jenkins hears the laughter—we find ourselves on her side.

Paxton caps an outstanding performance in the scene that follows.