Lena Sibony plays the title character in “Shoshana in December,” a new musical presented by Custom Made Theatre Company and Faultline Theater. (Photo by Jay Yamada/Courtesy Custom Made Theatre Company and FaultLine Theater)

There’s a short scene midway through the second act of “Shoshana in December,” a new musical making its world premiere in a Custom Made Theatre Company and Faultline Theater production. It’s between Shoshana (played with an appealing awkwardness by Lena Sibony), a young woman struggling to make a decision about her romantic life—and hence her life in general—and her loving and deeply understanding Jewish mother, Rebecca (delightfully underplayed by Sara Felder). Mostly sung by Rebecca, the scene is really the only authentic one in the entire musical—authentic because the relationship between the two women feels real, because the song’s lyrics are genuine and smart and because finally two characters are not straining to be funny or emotionally overwrought. 

Custom Made has produced some wonderful plays in the past, plays that explore complex relationships or themes. The recent “Zac and Siah or, Jesus in a Body Bag” by Jeffrey Lo is a fine example of a comedy about, well, dead Jesus, that was both funny and thoughtful. So although it’s admirable for the small company to stage a brand-new musical, it’s disappointing that this one, with book by Rose Oser, lyrics by Weston Scott and music by Matt Fukui Grandy, is so thin and so unambitious. 

Shoshana, in a loving relationship with musician Danny (a goofy Evan Wardell with guitar in hand), is tempted into a romance with the totally chill (and gentile) lesbian Cecily (a bland Kaitlyn Ortega), who’s polyamorous. Shoshana is understandably confused and uncertain about what she truly wants.  

When the seductive Cecily invites her to spend Christmas (a holiday that Shoshana, being Jewish, hates) in Los Angeles at her family’s home, Shoshana can’t resist. Danny, for his part, is focused on his career ambitions and doesn’t understand what’s really going on—nor does Shoshana have the courage to tell him the truth. 

At Cecily’s family home, everybody is gearing up for the holidays, which makes the already uneasy Shoshana more uncomfortable than ever. But the Jew-among-gentiles-at-Christmas subplot, so full of potential, feels extraneous, an excuse for general silliness rather than true social conflict: Shoshana doesn’t know how to decorate a Christmas tree; Cecily’s father (John Mannion, who plays multiple small roles) in a Santa outfit sings a song about—Santa. And a sex scene between Shoshana and Cecily feels rote and unconvincing. 

Despite the generally forced humor, there are moments other than the Shoshana-Rebecca scene that are truly entertaining, in particular a jolly Hanukkah song that Rebecca, Shoshana and Danny sing in Hebrew, interweaving their own personal English subtext into the traditional lyrics.  

And, were it not for the too-broad acting, there’s also a scene on an airplane involving an overly emotional, over-sharing stranger. 

But—not to put too fine a point on it—the actors, as directed by Vanessa Flores, are, for the most part, playing comic caricatures (and not all of them have the best singing voices); most of the musical numbers are forgettable; the choreography is unimaginative and often just silly; and at least on opening night the musical score was so loud that it was hard, even in this tiny venue and with the actors miked, to hear the songs’ lyrics. 

As too often happens in plays, once people stop keeping secrets and tell the truth—Shoshana to Danny and to herself; Cecily (but less successfully) to her mother—happy endings automatically follow. This is a thin premise for a play that is too busy trying to be funny to truly dig into its principal characters’ complexities.  

“Shoshana in December,” presented by Custom Made Theatre Company and Faultline Theater, continues through Dec. 18 at Phoenix Theatre, 414 Mason St., San Francisco. Tickets are $36-$45; visit custommade.org.