Bruce Leddy, who wrote, directed, and produced “Sing Now or Forever Hold Your Peace,” banked on the idea that just about everyone loves college a cappella. The soundtrack will be good, but music alone does not translate into a movie of substance. The shallow “Sing Now” is a fun few hours, but it can be difficult to watch when it tries to strike a serious note.

A film festival audience favorite, the movie was originally titled “Shut Up and Sing” in reference to the characters’ annoying habit of yelling “shut up!” at the drop of a hat. Maybe some people who graduated from college in the early ’90s really do scream at each other for fun, but the yelling happens to grate on my nerves. The new title certainly isn’t much more appropriate than the old one—the script’s wedding only serves as an excuse to reunite friends in vacationland.

“Sing Now” follows a closely-knit a cappella group that reunites 15 years after graduation to celebrate the wedding of its seventh member. After a narrated flashback of the cast singing with bad ’80s hair, the plot darts around to introduce us to six men and the women in their lives. Then we watch as they all drive by Long Island landmarks to a beach house owned by Spooner (Chris Bowers), the hot Buddhist astrophysicist of the bunch.

“Sing Now” is most engaging when it develops the friends’ personal stories. There’s the maybe-gay starving actor, the high-strung boring one with the loudmouth wife (played by the irritating Molly Shannon of “Saturday Night Live” semi-fame), the L.A. hotshot, the Manhattan lawyer divorcee, and the normal guy who keeps measuring his receding hairline in inches.

They’ve all got their idiosyncrasies and personal issues, but according to the movie, they can miraculously transform and produce beautiful a cappella harmonies to escape their worries. Sadly, the dubbing of studio-recorded a cappella just doesn’t fit with the footage of a group of rusty thirty-somethings practicing in the woods. It’s as if an Opportunes recording were played over a video of a First-Year Outdoor Program excursion—the two just don’t jive.

Most of the guys obsess over their ages, and the onset of their mid-life crises becomes the focus of the movie. Meanwhile, their wives and girlfriends form cliques, mock the men, and joke about swapping husbands. In fact, the characters refuse to discuss anything but sex and old age. The racy scenes spiral out of control until one of the men attempts suicide.

Without warning, “Sing Now” brings a serious moral theme into focus—marriage and life aren’t perfect, so all you Gen-Xers out there need to appreciate your thirties while you can still skinny-dip. Someday you really will be old.

The problem is, no matter where the script turns, the plot is frivolous. It’s a funny movie, but it’s uncomfortably lodged between the patently ridiculous and the irritatingly straight-faced.

“Sing Now” carries a strong summer-camp feeling of petty drama. But beyond the carpe diem attitude improvement, the film contains little real character development. Between entertaining romps like a stoned Frisbee golf game and sex fantasies about a Swedish nanny, “Sing Now or Forever Hold Your Peace” tries and fails to be serious.