"Souvenir" is a small, two-character comedy built on the improbable but historical career of a New York socialite with a horrendous singing voice.

Florence Foster Jenkins was a popular figure on the entertainment scene for a dozen years prior to her death in 1944. Comparisons to Tiny Tim and Mrs. Miller are appropriate, since Ms. Jenkins was blissfully unaware that she could not carry a tune. Audiences flocked to her recitals at the Ritz-Carlton Hotel ballroom to participate in their camp appeal.

The play by Stephen Temperley is characterized as a fantasy, told in affectionate retrospect by her accompanist, Cosme McMoon, 20 years after her death. While the concert appearances are based on fact, their intimate rehearsal and dressing room conversations are pure conjecture.

The difficulty in the script, born out in the current Diamond Head Theatre production directed by John Rampage and starring Stefanie Smart and Laurence Paxton, is that it's based on a single obvious joke.

For most of Act One, Ms. Smart sings horrendously off key, but with the utter innocence and confidence that added to Ms. Jenkins' appeal, while Mr. Paxton winces and grimaces. It is nearly an hour of fractured Mozart, Verdi and other classical composers, leaving the audience wondering "How much worse can she get?" and "Where does the story line go from here?"

Act Two answers both questions with Jenkins' Carnegie Hall performance at age 74.

While the croaking and the face-making continue on the same plane, costumer Peggy Krock decks out Ms. Smart in a series of flamboyantly tasteless outfits, culminating in a white taffeta gown and angel wings for Ms. Jenkins' signature "Ave Maria."

The saving grace that keeps the production from being simply a one-trick pony is the developing relationship between the singer and her piano player. While the soprano steams ahead with the confidence of an unsinkable ocean liner, the accompanist is perpetually rearranging seats in the life boats.

A failed songwriter, McMoon originally takes the job as a temporary paycheck. Jenkins makes him promise to tell her if she ever loses her "perfect pitch." That partnership lasted 12 years. Unable to stand his friends' goading, McMoon made other friends who were "less musical." Jenkins recorded an album that sold like wildfire.

While McMoon's motives might be suspiciously linked to a steady income and the chance to have his own compositions sung in public, he becomes protectively concerned as crowds grow from a circle of society friends to the general public, observing, "They look like they're here for a prize fight."

Ultimately, he assures her that she is loved by her audiences and rationalizes in an aside that "What's important is what you hear in your own head."

Smart and Paxton are well-cast in the roles. While she curiously makes little attempt to portray Jenkins' actual age (62 to 74), she is professionally able to sustain two hours of bad notes. Paxton plays his own piano and sings popular tunes between the flashbacks.

Designer Willie Sabel builds an elegant art deco proscenium and a grand apartment with windows overlooking a romantic city skyline. Lighting designer Stephen Clear signals the time jumps with bold changes in hue.