Katy Perry, “Witness” (Capitol)

Perry’s hair isn’t the only thing that’s shortened in recent months.

When the singer unveiled in February that she’d completed a new album, her first since 2013’s “Prism,” she used the phrase “purposeful pop” to describe the music. Such an expression suggested she had taken on a political edge following the election of Donald Trump. Given Perry’s established flair for cheeky party tunes such as “Last Friday Night (T.G.I.F.)” and vivid young-love songs like the immortal “Teenage Dream,” this felt like reason to worry.

Yet “Chained to the Rhythm,” the album’s lead single, turned out to be great: a sly condemnation of fake news that understands its own role in getting people to “dance to the distortion,” as she puts it over producer Max Martin’s shimmering disco groove.

But by April, Perry appeared to have lost interest in purposeful pop. Her next single was the raunchy “Bon Appétit,” complete with a regrettable buffet metaphor, followed by “Swish Swish,” her supposed takedown of Taylor Swift (who’d dissed Perry with 2014’s “Bad Blood”). Both failed to crack the top 40.

Now comes the full album, and it’s more jumbled still, with would-be self-empowerment anthems next to earnest ballads lamenting the end of a relationship; Perry’s many collaborators run the gamut from Martin to veteran bassist Pino Palladino.

Variety is a condition of modern pop, in which big-ticket albums are typically assembled by committee; sometimes the result even captures something of our addled era, as with Beyoncé’s dizzying “Lemonade.” But “Witness” diagnoses only Perry’s desperation for a hit.

“Hey Hey Hey” plays like a weak attempt to duplicate the success of her uplifting 2013 smash “Roar,” this time with a paper-thin tune and clunky words about being “Marilyn Monroe in a monster truck.” “Roulette” has a sturdier melody but none of the witty specifics of Perry’s earlier exhortations to cut loose. And then there are forgettable team-ups with hip-hop’s Mike Will Made It (“Tsunami”) and Corin Roddick of the Canadian indie duo Purity Ring (“Mind Maze”).

“Witness” contains strong moments beyond “Chained to the Rhythm.” Her singing is as forceful as ever in “Pendulum,” a gospel-accented number produced with real swing by Jeff Bhasker, while the slithering “Power” puts her vocals against soulful textures that draw out new grit.

And however petty its inspiration, “Swish Swish” is a delight as Perry rhymes “another one in the basket” with “another one in the casket” over Duke Dumont’s thrusting ’90s-house beat. But it’s hard to tell what each track has to do with the others, a problem this one-woman charisma factory has never experienced before.

MIKAEL WOOD, Los Angeles Times

new releases

• Lorde, “Melodrama”

• Beth Ditto, “Fake Sugar”

• Fleet Foxes, “Crack-Up”

• Jason Isbell, “The Nashville Sound”

• Big Boi, “Boomiverse”

• 2 Chainz, “Pretty Girls Like Trap Music”

• Steve Earle, “So You Wanna Be an Outlaw”

• Nickelback, “Feed the Machine”

• Alison Moyet, “Other”