What do you do when you want to hang out with your new best friend, but she lives 10,000 miles away on the other side of the world?

If you're Kurt Vile in Philadelphia and Courtney Barnett in Melbourne, Australia, you do what comes naturally: You make a record together and go out on tour.

Thus, we have Lotta Sea Lice (Matador ***), the thoroughly charming collaborative LP with which the two hirsute indie stars surprised their fans when it was announced this year.

The two guitarists have been on a U.S. tour with their Sea Lice backing band, and they will arrive on Friday at the Tower Theater in Upper Darby, just down the road from where Vile grew up in Lansdowne. Barnett's partner Jen Cloher, whose Neil Young & Crazy Horse-ish "Fear is Like a Forest" she and Vile cover on Lotta Sea Lice, opens the show.

The relationship between Barnett and Vile — who bill themselves in alphabetical order in part to minimize Kurt and Courtney chatter — began with Vile's 2011 album Smoke Ring for My Halo.

For Barnett, who will turn 30 the day of the Tower show, that album played a crucial role in forming her musical identity.

"I had just moved to Melbourne,  and I was discovering this whole new world of music," she says, talking on the phone along with Vile from a tour stop in Portland, Ore. "Like Neil Young, who I had never listened to until I was in my early 20s.

"I went to the record store and said, 'What's a good record?' The guy said, 'How about try this one?' It was Smoke Ring, and it was like nothing else that I'd been listening to. It just blew everything away. It's so gentle, and I really connected with a lot of the lyrics. That's why I did the 'Peeping Tomboy' cover" — whose title she changed to "Peeping Tom" on Sea Lice. "Kurt's weird phrasing kind of reminded me of the way I was writing songs, and I liked that. It drew a little line between us."

Barnett went to see Vile and his band the Violators when they went to Melbourne in 2011, and the time after that, in 2014, she opened for them. They met briefly after the latter show, and she gave him her 2014 album-length release The Double EP: A Sea of Split Peas.

"I really liked that album she gave me," says Vile, 37. "And then her next album" — 2015's Sometimes I Sit and Think, and Sometimes I Just Sit — "I also liked that a lot. I just wanted to do a song with her. My favorite song was 'Depreston,' but I was listening to her whole record and I was really into her lyrics and her voice. And I just thought it would be awesome if I could pull off a duet with her."

Vile wrote "Over Everything," the lead single from Sea Lice about blues guitar riffs and the importance of wearing earplugs to guard against tinnitus. It features an amusing video in which Barnett lip-syncs to Vile's vocals and vice versa. "I basically wrote the song as if she already said yes. She didn't know yet that she was going to be on it, but I knew. At least, that's the way I wrote it. As if she did."

Sea Lice — which takes its name from an inside joke told by Warpaint's Stella Mozgawa, who will be drumming for the duo — was recorded in Down Under studio sessions preceding Vile's Australian tour during the American winters of 2016 and 2017.

At first, the plan was to do one song, then a split 7-inch — that is, a two-sided 45 rpm vinyl single. Things went so swimmingly, however, that eventually it turned into a nine-song album, with a bunch of new songs like "Over Everything," the moody "On Script," and goofy "Blue Cheese."

Leaning more to Vile's Zen-like chill than Barnett's garage-rock template, the artists also cover each other's tunes, with Vile essaying Barnett's "Out of the Woodwork." They team up on "Untogether," by Tanya Donelly's 1990's Boston alt-rock band Belly. Intriguingly, the duo also took on Fats Domino's "Blueberry Hill" but left it off the album. You'll have to wait for the deluxe edition for that one.

The warm, inviting vibe on Sea Lice begs to be called conversational. Barnett and Vile communicate back and forth in guitar licks and spoken-sung lyrics that might be drawn from phone calls or other forms of hemisphere-crossing digital communication.

"When we were away from each other, we were keeping in constant contact," says Barnett. "I would take note of our conversations and draw them out and see what they would turn into. There might be a fleeting phrase of a throwaway line that you put in the context of a song and it translates into something bigger."

Just as they do in Sea Lice's songs, Barnett and Vile take up each other's thoughts. "We also live in a very texty world now," he says. "So we can make these jokes and keep them for later. You're writing them down anyway."

That casual, collaborative process is the subject of Sea Lice's offhand-sounding "Continental Breakfast." "I cherish my intercontinental friendships," Barnett sings over a pretty, fingerpicked melody. "We talk it over continental breakfast, in a hotel in East Bumble, Wherever." Then Vile's Philly drawl comes in to remind us what a small world it is: "Somewhere on the sphere, around here."

For a video, director Danny Cohen — who also took the press photos that show Barnett and Vile looking like they might be twin siblings conjoined at the hair — had a hard time getting time commitments, as both Vile and Barnett were spending pretour time with their families. "I was like, 'I got to catch up with my grandma,' " said Barnett. "And Kurt was like …" He completes the sentence, "… I have to go to my daughter's horse-galloping contest."

The solution was to follow each of the singers around in intimate settings. In Melbourne, Barnett is at home with Cloher, and visiting with her mother, grandmother, and a close friend's infant. Vile is on camera at his house in Mount Airy with his wife, Suzanne, and their two daughters, as well as strolling through the Wissahickon in Fairmount Park and on the boardwalk in Ocean City, N.J., where he's written several songs in recent years. It's adorable.

After the tour ends in in Austin this month, the two don't have any immediate plans to work together again. There will be another album "in our lifetime," though, Vile says. Chuckling ensues about what they might sound like in their 60s.

But for now, the far-flung friends are just enjoying the opportunity to play music together in the same time zone and place.

"It's been getting better as it goes," says Barnett. "It's a whole new band, a whole new thing. It's just nice having Kurt on stage, smiling at each other."
"This is a really good thing," says Vile. "It's definitely not going to get dark, I can tell."

MUSIC

Courtney Barnett & Kurt Vile

  • 8 p.m. Friday, November 3, Tower Theater, 69th and Ludlow Sts., Upper Darby. Sold out. 610-352-2887. livenation.com