Part of that came from a grander ambition, a willingness to go beyond the folked-up strummings of Letters to Rome into indie rock and alt-country without ever abandoning the thrill of melody. Now, on There is a Vine, released next weekend with shows in Rockland and Portland, the band have returned to the religious introspection of Rome while edging even farther from their comfort zone with an aggression you haven’t heard before from Tree by Leaf. It may not deliver as many warm fuzzies as Black and Blue, but it’s more challenging and thought-provoking, and it retains all of that album’s literacy and wit.

Garrett writes all but one of the new songs, and it’s safe to say he’s one of the best lyricists working today. He creates couplets you’re shocked you’ve never heard before (“It’s better to forget than to live with regret”) while dropping the sublime almost effortlessly (“Now he wishes her well, may she live long and prosper/And his is a glow, now, like Madonna’s penumbra”). Couple that with his heart-felt delivery, enough to get you worried for the veins popping out of his neck, and it’s nearly impossible not to be sucked into his tales of existential deliberation.

Nearly every song here deals with humanity’s relationship to God. Right from the album’s outset, the rollicking piano and raucous drums of “Over and Under,” Garrett wonders, “what is delusion?/What is devotion?” And these are questions to which he won’t offer easy answers, just interesting ways to say, “let’s talk about it,” like, “On the end of my cigarette, I’m gonna build a fire/And then we can burn this language down through the telephone wires.”

One thing they know for sure about God? He’s better than George Bush and those who would claim God for their side, and so “His Banner Over Us Is Love” is one of the better protest songs you’ll hear this year. Over a manically strummed acoustic guitar, Garrett declares himself no patriot because he knows “a king whose flag is true, and his spectrum holds no red or blue.”

This isn’t to say, however, that Tree by Leaf have abandoned the love song. “Come on, Babe” delivers again on the promise held out by the sensational “Rupert Sheldrake’s Girl” from last year. With its piano and roadhouse drums, some harmonica and simple bass, it feels, as with much of the album, like a song built for an out-of-the-way bar where a few couples dance with beers behind each other’s back, and the bartender isn’t disappointed if only 15 people walk through the door all night because he knows every one of them by name and hopes he doesn’t have to drive them all home at the end of the night.

“Come on babe and call my bluff,” Garrett sings, just as desperate as he needs to be, “I’m ready to come home/Punch out the numbers and dial me up/I’m waiting by the phone/This is not the Enlightenment babe, this is resting just above/This is not the Romance babe/this is the renaissance of our love.” Okay, so the whole artistic-eras thing looks a little cheesy in print. Trust me, it sounds pretty damn great. And I think you’ll be won over later by the Sampson reference, too.

This song also features an interesting mix, with the acoustic guitar strum way to the bottom behind a piano break from Cliff Young, the trio’s third leg and rock-solid throughout. The guitar is just a little ahead of the beat, though, quickening the heart for the otherwise restrained piano. It’s good work from Bruce Boege, of Northport’s Limin Studios, but there are other places, particularly on “Over and Under,” where the instruments are muddy. Of all the good choices he makes, keeping Garrett and Siiri well to the fore is generally among them.

Siiri, who wrote a few of the songs last album, does get room to shine here. Her first bit is the slow and sedate “Chicago at Night” (written by yet another Soucy, Erica, Garrett’s sister, who plays solo and with Jet Black Dress), where she seduces like a siren over slide guitar and well-placed snare hits. Later, she delivers her most aggressive take yet, on “Little Lost and Lonely” moving from Norah Jones to something close to Mariah Carey by the song’s crescendoing finish.

For denouement, Siiri dials it back, paired with a harmonica, to demure, “it’s only me/Little lost and lonely.”

Sorry, but that’s not going to work anymore. Tree by Leaf are a standout talent and they very much carried expectations into this album. That they delivered without playing it safe should make everyone that much more eager for their next effort.