The Brooklyn trio Joan as Police Woman sumptuously broadens its musical palette on its new album, “To Survive” (Reveal), something the Louisville, Ky.-based quintet My Morning Jacket tries but fails to pull off on its own new record, “Evil Urges” (ATO). The latter group, led by singer-songwriter Jim James, wants to spice its Southern rock with more recombinant pop, experimenting with hip-hop beats, doo-wop moods, and arresting shifts of tempo, but the result sounds too strained and cumbersome. On “To Survive,” however, Joan as Police Woman builds on the slinky torch songs and folky jazz that the group introduced on 2006’s “Real Life,” confirming the group’s leader, Joan Wasser, as a singer-songwriter to whom experimentation comes effortlessly and organically. Both albums are out today.

“To Survive” isn’t merely a successful pop hybrid; it’s a disarming album that recalls the raw emotions of Cat Power’s early work, only set in much more plush, but never over-polished, arrangements. The album moves from stumbling misanthropy to ethereal pop to Patti Smith-like rock. And the group moves through these styles without ever losing its identity as an agile, dramatic combo.

Such stylistic acumen isn’t a surprise coming from Ms. Wasser. Trained as a violinist, she began displaying her knack for casual reinvention while playing the violin with a punk-like abandon in the 1990s college-radio rock staple the Dambuilders. Her Dambuilders work soon earned her studio time alongside a wide swathe of musicians, from Lou Reed and Sheryl Crow to Antony and the Johnsons, Sparklehorse, and Rufus Wainwright.

Ms. Wasser, who is backed by bandmates Rainy Orteca on bass and Ben Perowsky on drums, brings that considerable résumé to her own songwriting with “To Survive.” The trio has the limber feel and mood of a tight jazz trio, with Ms. Wasser backing her own vocals on piano, guitar, and violin. The trio plays her often jaunty tunes with a loose joy.

That casual attitude is one of the strongest elements of “To Survive.” Like Ms. Wasser, Ms. Orteca and Mr. Perowsky are veteran studio and touring musicians, and they bring a versatile confidence to Joan as Police Woman’s sprightly music. The late-night ballad “To Be Loved” would be a disaster in less capable hands. A romantic, nostalgic song about learning to accept happiness, the tune bubbles along at a whimsical pace, the drums and bass walking hand-in-hand behind Ms. Wasser’s husky falsetto and hesitant piano. It’s the sort of song and sentiment that could drift into empty cliché, but the band tempers that possibility by dusting the overwhelming uplift with bittersweet shades. Ms. Wasser never pushes her voice into a drunken upper register, which reins in the sentimentality, and a hovering electric guitar line tethers the melody to the ground. The song ends up feeling like a woozy 1960s Brazilian love song chilled and strained through a knowing resolve.

The song is followed immediately by its own opposite, “To Be Lonely.” A solitary piano opens the track, tracing what sounds like a few of the same melodic notes in “To Be Loved,” this time stretched and held to let their somber mood color the room. When Ms. Wasser comes in, singing in a husky breathiness, her vocal control lends this song’s more movingly melancholic lyrics — “this is the one I would die for / to be lonely with” — a ravishing beauty.

It’s a dazzling touch the trio pulls off in piano-driven songs such as the title track and the wonderful “To America,” on which Ms. Wasser plays her ornate words off her elemental music, sounding like Tom Waits in a cocktail dress. Such earthy flair and deft nuance permeate “To Survive,” an album whose mid-tempo, yearning melodies feature moments of surprising hope and pensive smiles. It’s a disorienting, pleasurable album, with Ms. Wasser’s winning, nimble presence holding everything together.

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My Morning Jacket isn’t nearly as successful as Joan as Police Woman at working its experiments into its strengths. This quintet earned its fan base by folding jam-band excursions and psychedelic touches into its fairly straightforward Southern rock, which the band has always delivered triumphantly onstage. But on its last album, 2005’s “Z,” the group began to try out a few new touches, incorporating synthesizers and adding a handful of dub-like rhythms to a few songs.

For its fifth studio album, “Evil Urges,” My Morning Jacket sounds as if it’s trying to pull a mid-career shift, à la Wilco’s “Yankee Hotel Foxtrot,” the 2001 album on which Jeff Tweedy almost completely reinvented his band’s sound. The ambition is admirable — such a radical change is extremely difficult for even a modestly successful act such as My Morning Jacket — but it doesn’t work in this instance. “Evil Urges” isn’t a bad album; it is merely one on which the band sounds lost in its own web of ideas.

Credit Mr. James for aiming so high. My Morning Jacket tries on almost every shade of pop available, from glam-rock funk (“Highly Suspicious”) to symphonic pop (“Two Halves”) to something like new wave (“Touch Me I’m Going to Scream”). The band gets through it all with workmanlike aplomb, but loses something in the process: its sense of self. Gone is Mr. James’s haunting, immediately identifiable wail, which he trades for flirtations with falsetto or letting other band members sing. Gone are the devilishly opaque lyrics that felt like Southern rock going prog in favor of simple stories and simple feelings. Gone are the slowly mounting sonic layers that build to operatic catharsis. Instead, “Evil Urges” sounds like an album that could have been made by any capable rock band. That it’s a My Morning Jacket album feels like an afterthought.

It’s an impression that’s most pressing when the band returns to its strengths. The country-fried space-rock of “I’m Amazed” and the down-tempo acoustic workout “Look at You” are the sorts of songs Mr. James and his bandmates typically hit out of the park. The cloud-like mix of pedal-steel guitar and dreamy acoustic strum on “Look at You” provides the perfect isolating backdrop for Mr. James’s voice, and the Neil Young blast of “I’m Amazed” offers the sort of plugged-in potential that the band loves to unleash onstage. It’s too bad that, in both instances, Mr. James sings trite, quasi-political songs that border on the sacred without sounding sincere. Religion, the South, and politics do mix in rock — see the Drive-By Truckers for a stellar example — but until My Morning Jacket figures out how to explore those subjects in its own voice, its efforts will only sound like a diluted version of its better work.