★ ½

The Pitch Perfect aca-franchise is ending, you awesome nerds. And unfortunately, the initially promising series went out on an overstuffed, off-tune whimper rather than a roar of sisterhood. The beloved Barden Bellas succumbed to the classic curse of the third installment.

Like many three-quels before it -- Spider-Man 3, Little Fockers, The Fast and the Furious: Tokyo Drift, etc. -- the third Pitch Perfect went entirely off the rails, mostly due to a tenuous story from co-screenwriter Kay Cannon. Cannon, who also wrote the scripts for both the original and Pitch Perfect 2, was apparently fresh out of ideas here: She throws a dozen tired tropes and bizarre diversions at the audience, just hoping one will stick. The reason people follow these films in the first place is the sense of female friendship, which was made an afterthought in the name of the finale being a big-budget blockbuster.

This 93-minute film is more or less an overlong epilogue for the characters, combined with a short foray into action comedy for Fat Amy in what feels like scenes from her straight-to-VHS spin-off. The movie’s only clever moments are callbacks that point out the franchise’s own flaws, such as everyone constantly ignoring Jessica and Ashley. (Who? Exactly.) Those moments can also be some of the most cringeworthy. The film practically Fat Amy’s itself by pointing out its flaws before you can -- but sometimes that’s just sad rather than funny. Cannon basically admits she was just too lazy to write a good scene by having a character bluntly lay out an entire scenario, followed by Flo saying, “That’s a lot of exposition!”

The rest of the film’s humor comes from characters saying awkward things, then waiting for the audience to laugh from discomfort. Look, Aubrey is starved for affirmation! Amy is hypersexual! Chloe is overemotional! Lilly is weird! In these moments, the secondary characters feel like they’ve devolved into caricatures of themselves (while some of them were caricatures to begin with). The only person who still comes across as charmingly quirky is Anna Kendrick’s Beca.

Thankfully, just when you realize you haven’t laughed in an uncomfortably long time, the film provides a much needed break to let the ladies sing. Kendrick and Ester Dean shine in the Bellas’ cover of “Cheap Thrills,” while the group’s performance of “Toxic” employs cool layered vocal sound effects. The movie’s only good use of the Bellas being on tour with a bunch of bands is the riff-off. The otherwise wasted rival musicians, more or less led by everyone’s girl crush Ruby Rose, keep the format interesting by mixing hip-hop, rock, and country styles, seriously crushing the Bella’s absurd themes (such as “zombie apocalypse songs”) by incorporating their instruments. It’s “cheating” according to the Bellas, but it’s an effective way to mix up the riff-off formula.

The new characters that are introduced here (all of the musicians, a military hunk, a dreamy producer, Amy’s dad) are nothing but two-dimensional stereotypes that are supposed to wrap up loose ends for the ladies, but are ultimately just filler. The Bellas don’t have time between flirting and country-hopping and fight scenes and explosions for any conflict or growth between them. Their successes are all basically handed to each of them, so the big finale of everyone supporting one another is unearned and the closing number, George Michael’s “Freedom! ’90,” packs no real emotional punch.

What will really touch those who’ve been following the franchise is the behind-the-scenes footage that runs alongside the credits. It’s a montage of the Bellas from all three movies goofing off on set and making memories together. It’s sweet and genuine and simple -- everything Pitch Perfect 3 isn’t. The Bellas’ bond and singing chops are enough for the film to be bearable, but it’s not worth watching unless you’re already a big aca-fan who wants closure.