It’s not often that we get two movie musicals opening in wide release in one week, and they could hardly be a greater study in contrasts. “The Greatest Showman” is an old-school tuner that brought in estimable stage-and-screen songwriters for an all-original song score that’s meant to convey the emotions of the characters and send our hearts soaring. “Pitch Perfect 3,” meanwhile, is a random jukebox musical that probably reaches peak soulfulness about the time we’re watching a group of beautiful young women sing DNCE’s “Cake by the Ocean.”

As somebody with a rooting interest in the kind of old-fashioned movie musicals where song is actually connected to plot, I’d hoped to report that the 10 new “Greatest Showman” tunes win this Barnum-and-Bellas sing-off. But as much as I’m a fan of keeping that form of movie music alive, I’m an even bigger fan of the honest power of a hit. “Greatest Showman,” bless its heart, doesn’t have any. “Pitch Perfect 3,” meanwhile, has an enduring one: “Toxic,” the one song you can be certain moviegoers will be humming on their way out of the megaplex this weekend.

The greatest soundtrack showman of the moment, then? Sorry, P.T.: It’s Britney, um, bitch.

That’s not to make any particular claims for “PP3” as a film, but to point up how a great song can make even a lame movie feel exhilarating. The filmmakers seem to have realized it: Although the Bellas’ song-and-dance version of “Toxic” pops up at the climax, it’s also seen at the beginning, in a flashback structure that was probably added in post-production. The scene itself couldn’t be more ridiculous: The a cappella group is executing maniacal choreography aboard villain John Lithgow’s yacht to distract him from explosive charges being set. It has the effect of distracting us, too, from wondering why anyone thought building a kidnapping/action plot around the Bellas was a good idea. Now, as in 2014, when Spears’ version became a smash, it’s impossible to not get the kind of buzz off the song that wipes good sense clean away.

At the risk of giving the filmmakers too much credit for cleverness, there is a subtle craftiness to the way the “Toxic” scene is set up, musically. It’s preceded by the sight of Anna Kendrick and Rebel Wilson motoring out to the yacht to rescue their comrades. The element of intrigue is signaled by a bit of suspenseful music that echoes classic James Bond soundtracks — orchestration mixed with twangy guitar. Spears’ original version of “Toxic” had those elements, too, with that Bond-ian guitar at the end, though the faux strings were more Bollywood than Hollywood, and the entire thing was revved up to 500 bpm. In the Bellas’ version, they (or whatever choir was in the studio) do the string and guitar parts, vocally. It’d sound fun even without the accompanying sight of a whiplash chorus line.

Dozens of lesser songs pop up, individually or as medleys, in “PP3,” though each musical moment tends to be an okay emulation of something that was more effective in the first two movies. The first one had Kendrick’s “Cups” song, the second one had Hailee Steinfeld’s breakout number, but this final entry curiously gives the only original song, the rocker “How a Heart Unbreaks,” to a rival group, Evermoist, led by Ruby Rose. In the big freestyling sing-off competition, there are categories like songs by writers you didn’t know were Jewish, or songs for the zombie apocalypse… not much of a joke compared to the previous movie’s medley of singers who’d dated John Mayer. The film’s other big musical climax, after “Toxic,” comes when the Bellas band together for an impromptu-yet-nonetheless-perfect rendition of “Freedom ’90.” It’s supposed to be their sentimental swan song, and it’s okay, but it’s hard to come down from “Toxic,” even for George Michael.

It’s kind of hilarious how much “PP3” has been cut down to the bare essentials. All the men in the movie, even Lithgow, seem to have had their parts but out of the movie, because at some point the filmmakers realized, correctly, that we just want to see eight beautiful female actors with strong comic chops riffing through the one-liners that reflect the single character traits they’ve been given. All the exposition and subplots have apparently been trimmed out, too, in order to cram as much music as possible into the film. As a movie, it’s a mess. But as a delivery system for a nearly non-stop barrage of sweetly harmonized cover songs, it’s still kind of a kick. So if this diminishing-returns entry really is the end of the line for the Bellas — and there aren’t many scenarios you can come up with where a group of eight women in their 30s will face large, adoring audiences as a chorale — I’m going to miss them.

I won’t mourn the lack of any “Greatest Showman” sequels. It feels like a lost opportunity: When was the last time we had an all-new, non-theatrically-based movie musical with 10 songs written expressly for the screen? (This is not a rhetorical question. Write in if you can think of one.) And songwriters Benj Pasek and Justin Paul should have been up to the task, with “Dear Evan Hanson” and “La La Land” on their resume. You’re tempted not to blame them for the results: Surely someone in the production gave them the instruction to write a collection of inspirational bromides that sound like they would have been in Celine Dion’s reject pile in 1995.

There are two numbers that at least stand out amid the treacle. Although it’s not great, the big, showy Jenny Lind ballad, “Never Enough,” at least benefits from being written for the movie’s one non-virtuous character, and from the camera concentrating on Loren Allred’s face as much as it did on Emma Stone’s when she sang their “Audition” in “La La Land.” And there is the real showstopper-by-design, “This is Me,” which is basically this movie’s “And I’m Telling You I’m Not Going,” but more upbeat, because the bearded lady who sings it actually isn’t going anywhere.

It feels like you’re not on the side of the angels, if you argue that a ramshackle collection of cover songs in a goofy, less than expertly made comedy beats the high-minded stuff that’s meant to remind us to all follow our dreams. But at the end of a toxic year, it’s clear what we really need, and it’s not pained earnestness. It’s “Toxic,” the razzle-dazzle, all-that-jazz show tune of 2017.