By Carolyn Hayes Harmer

It is a truth universally acknowledged that, once assembled, a collective of otherwise adult women must slam alcoholic drinks and shriek about phalluses, the timber of their voices rising with amassing inebriation and girl power. The bigger the group, the easier it is to get swept away into loud and lewd territory. This is why “Girls Night: The Musical” insists on being an active viewing experience, rather than a passive one. The production now at the City Theatre encourages its female-targeted audience to let loose en masse, allowing the performers’ and spectators’ energies to feed off each other to reach peak feminine frenzy.

The show is prefaced by a spirited address from Sharon (Erin Schaut), who banters with the crowd and encourages singing, dancing and liberal WOO!-ing. (Drinking in the theater is also permitted, but the prominent bar just outside the entrance is apparently invitation enough.) Schaut’s easy back-and-forth with the lubricated masses also opens the door for hollered commentary – curveballs that only seem to increase in frequency the better she comically defuses the interruptions. Within the story, Sharon functions as omniscient narrator extraordinaire: Clad in marabou-trimmed angel wings, she explains that she is actually long dead, but thrilled that her old friends (who cannot see or hear her) are gathering to celebrate the news of her daughter’s engagement.

The friends are certifiable but sincere Anita (Kelly Higgins), rich and scathing Liza (Sarah Lynn Robinson), commanding social maven Carol (Missy Aguilar), and Carol’s unfortunate tagalong younger sister, Kate (Katie Campbell). They meet at a club for drinks and karaoke, the better to belt out their feelings to a backing track of throwback anthems about womanhood, attraction and heartbreak. Vocally, the performances are on par with very skillful karaoke, often supplemented by strong backup singing and/or indifferent choreography.

Between songs, there are girly shenanigans aplenty, including anatomic overshares, heaps of smack talk, titillating bachelorette-party accessories, light profanity, and one incredibly sloppy drunk. Although the overall tenor is rowdy and – for lack of a better word – broad, the facile writing also skids far afield to take limp swipes at serious topics, such as marital strife and mental health. Some of these come-to-Jesus moments take place in the ladies’ room of the club, others in disjointed flashbacks that show off the worst of the slapdash add-a-layer costume design.

But where the production fails as theater (with patchy lighting design, overblown audio, and script and direction reminiscent of a high school pep rally), it succeeds as a kind of conducted party, fostering an atmosphere that safely permits some ribald behavior and much revelry. The ensemble cast keeps the energy thrumming, leading the throng by example and letting its talents show. Given the most variation as the inadequately medicated quirky one, Higgins’s performance is a standout, highlighted by a blazing torch song. Yet the spark behind the character is integral to elevate this material, and here every last actress delivers – Aguilar in particular finds little ways to have fun within the bounds of the play, and it shows.

“Girls Night” is a unique piece of entertainment, one that (like the tradition for which it’s named) only works in plural form. If the opening-night audience is any indicator, the production has a special knack for rallying an audience predominated by women and shepherding it into a freewheeling evening of shared fun and fervor. This is the kind of show best appreciated among a posse of like-minded girlfriends: The bigger the party, the better.