Advocates of marriage equality, take note: One of this year's entries at the New York Musical Theatre Festival might just rank as the most tuneful weapon you'll ever find for advancing your case. My Mother's Lesbian Jewish Wiccan Wedding, which was written by husband-and-wife team David Hein and Irene Sankoff based on Hein's own double-mothered upbringing, boasts tunes of immense likeability that ring in your ear far more delightfully than the most melodic of political tracts can usually manage. Hein and Sankoff would have it made if that's all it took to make a great musical. It isn't, of course, and it's in the yawning grey everywhere else that this production, which has been gamely directed by Stafford Arima, stumbles, spills, and stagnates.

The promise and the problems are inherent in the title, which advertise a show Hein and Sankoff apparently have no desire to deliver. What you might (rightfully) think would be an epic (and uproarious) clashing of worlds is spun time and time again with a ceiling-shattering shrug. Presented as an evening's entertainment on Open Mic Night at the Cat Scratch Club, the show centers on the guitar-playing narrator, David (Hein), who just can't wait to tell you about his moms. And tell he does, from beginning to end, without showing you much beyond the titular ceremony that comprises the final (and least interesting) seven minutes of the show.

What you don't see is the full evolution of David's mom, Claire (Liz Larsen), from a straitlaced and, well, straight Nebraskan who discovers her true yearnings after she divorces and moves to Ottawa. By the end of her first meeting with the new love of her life, Jane (Ann Harada, of Avenue Q fame), the pair has already kissed, Jane has already sold Claire on Wicca, and there's nowhere for either of them to move except in circles while we wait for the inevitable nuptials and the predictable obstacles that prevent them from occurring for about 85 minutes.

Sure, there's Claire coming to terms with the Judaism she abandoned as a young girl, but even that turnaround happens offstage and is described only after it's concluded. It's the journeys that are missing, and without them the show feels more like a torn pamphlet than a passionate personal diary. We don't need the chorus to have so many songs about Ottawa, or for Claire's ex (Bart Shatto) to lead a doo-wop quintet about how hot it is that his former wife is now sleeping with a woman, or a hoedown set in Hooters (because David thought that the owl logo heralded a family-friendly establishment—yeah right), or even an astonishingly lengthy musical showpiece near the end of the show called "Short History of Gay Marriage," which describes—well, you know.

This is all forgettably enjoyable, but it's local color when we need deep psychological and spiritual exploration. Without that, there's nothing to stop the show from feeling shallow whenever it's not crusading for gay marriage. Larsen and Harada are as personable and talented musical comediennes as you'll find, but they can provide no reasons to view Claire and Jane as anything but symbols of a movement. The only chance the actresses get for genuine connection occurs late in the evening, in a number called "Nebraska," which finds Claire railing against the state she couldn't wait to escape but that Jane wants to embrace as the place that produced the woman she adores. That's real, tangible conflict, and the song's gradual transformation from angry screed into a tender love song is the kind of theatrical magic the show otherwise shuns.

In fairness, this isn't a show about doing things the old, trusted ways, and as it emerge from the Toronto Fringe Festival, that aesthetic has doubtlessly been built into the structure from the start. But promoting an agenda is simply not the same as charting souls. Ultimately, it's almost always rich humanity rather than worthwhile causes that inspires great moments, great scores, and great musicals—and that's what's most missing here. That the wedding itself feels like an afterthought, more of a burden of obligation than an execution of joyful dramatic necessity—the true climax occurs a couple of scenes earlier, when Canada legalizes gay marriage in 2005—tells you everything you need to know about where this show's heart really lies. Or, more accurately, where it doesn't.

Intoxicating as the music may be, it can't compensate for a story and characters that rarely express themselves openly, and then only do so in lyrics of light-landing sentiment, casual attention to proper stressing, and only moderate attempts at perfect rhymes. Perhaps you could forgive all or some of this if the content of what's there were unassailable, but that's not the case, either. The finale, for example, turns on the work's title sung repeatedly, as if to ensure that you'll never forget the name of the show you've just seen. Considering how little of My Mother's Lesbian Jewish Wiccan Wedding gives memorable voice to people and situations we've never been exposed to before, that was probably the wisest of the few concrete choices Hein and Sankoff made.

­­My Mother's Lesbian Jewish Wiccan Wedding
Tickets online and current performance schedule at The New York Musical Theatre Festival