The harmonies brought Sheila Carabine and Amanda Walther together.

One of Carabine’s earliest memories of Walther, her bandmate in folk duo Dala, is singing Beatles songs together in the hallways of their Catholic high school in Toronto. They met when Carabine was 15 and Walther was 17, bonding over a shared love of music and their complementary vocal ranges — Carabine is an alto, Walther is a soprano.

“I was in grade nine and Amanda is two years my senior, so she was the rebellious, blue-haired girl in our high school,” Carabine said from her home in Toronto about a week before Dala’s short West Coast tour that kicks off tonight at the Tower Theatre. “And we met in our jazz band class, so she was the jazz singer singing Frank Sinatra, and I was playing trumpet.”

By the end of their time in high school, they had written their first song together, “Paul’s Song,” about a mutual friend. Naturally, they built the song around their vocals.

“We wrote the harmony and the melody at the same time, and that was really what informed the lyrics,” Carabine said from her home in Toronto. “It was kind of hard to say where one part of the process started and the other part ended; they’re all happening in tandem.”

Nearly 14 years later, and the writing process is about the same for Carabine and Walther. Even as the duo’s albums have grown more instrumentally complex — culminating in the swelling string arrangements on 2012’s “Best Day” — the focus has remained on the melodies, harmonies and lyrics. In fact, Carabine said the songs have to stand on their own a cappella.

“I think you work within your limitations,” Carabine said. “There’s a great line about, I think it’s a Robert Frost quote about his idea that writing poetry without a rhyming scheme or a rhythm scheme was like playing tennis without a net. You kind of need the parameter to work within. How I translated that into our writing process is, I have a certain vocal range that I write within, but Amanda’s vocal range, she’s a soprano, so that kind of extends that, and we work within that. But the songwriting, the core of it and the kind of basic principle is about harmony for us.”

This same vocals-first approach has also helped elevate Dala as one of folk music’s premier song interpreters. In 2010 the PBS live special “Girls From the North Country,” featuring the titular Bob Dylan cover alongside originals and covers of Neil Young, Joni Mitchell and Gordon Lightfoot, earned Dala a Canadian Folk Music Award for Vocal Group of the Year. The live album release subsequently won a Juno Award.

“In the beginning (covers were) a way of getting the audience’s attention; audiences that knew nothing about us, it gave them a reference point as far as our style and our approach,” “And now we’re very selective about the covers we’ve started to do. We’re doing an Arlo Guthrie cover, ‘Coming Into Los Angeles,’ which is so fun. And it’s a way for us to kind of have fun; we’re just having fun with songs that we love and perhaps shedding a new focus on the lyrics or the melody with our unique approach.”

Dala has been mostly quiet on the writing and recording front since “Best Day,” which also earned the group a trio of Canadian Folk Music Award nominations. However, the duo recently posted a video to their website in February of an untitled, new composition inspired in part by a songwriting email chain run by songwriter Matt Sever, better known as Matt the Electrician of Austin, Texas. The two met Sever at their first, and to date only, appearance at the Sisters Folk Festival in 2011 — which Carabine called “one of the highlights” of Dala’s many festival visits across the U.S. and Canada.

Those festival trips continue unabated — the duo is already booked for Musikfest in Bethlehem, Pennsylvania, and the Kerrville Folk Festival in Kerrville, Texas, this summer. In 2009, Dala was the only Canadian group to perform at the 50th anniversary edition of the Newport Folk Festival.

“It was like the Olympics, we were like the bobsled team,” Carabine said, recalling the festival. “I’ll remember that until my winter years; that was an amazing experience. There was a moment where Amanda and I were just backstage just kind of like flies on the wall. We watched Judy Collins and Joan Baez high five each other, and Pete Seeger was there, and we saw the Fleet Foxes, one of my favorite bands. It was just a feast for your ears and your eyes.”

But before the festival season starts, the duo heads West this month for dates in Seattle, Alaska and of course Bend (“It’s part tour, part vacation,” Carabine said).

In addition to touring, Carabine and Walther have kept busy with other projects. Following the birth of her first child two years ago, Walther recorded the children’s album “More Better” with her brothers and cousins under the name WWClub.

“We’ll be bringing that one with us,” Carabine said. “Her kid’s album is called ‘More Better.’ There should be a disclaimer: not educational.”

Carabine will also release her first solo album later this year. At around the same time Walther recorded with her family, Carabine spent time in the Maritimes on the east coast of Canada immersed in French Canadian music and culture. The experience inspired a new batch of songs, including an adaptation of a W.B. Yeats poem.

“It was just really inspiring; I felt like I got to hear my own thoughts, hear my own voice a little more clearly than normal,” Carabine said.

Walther sings harmony on the album, prompting Carabine to joke the record should be called “Lada” — an inverse of Dala’s combination of Sheila and Amanda. But Carabine has already performed a number of solo shows in support of the album. Stepping away from her childhood partnership with Walther has been nerve-wracking for Carabine, to say the least.

“It’s made me appreciate even more how much I enjoy the chemistry that Amanda and I have onstage, and how in moments when we’re playing a new venue and we might be a bit nervous, we just turn to each other and make each other laugh, and that’s very reassuring,” she said. “I’m so used to having her playing left wing with me onstage. And now the few shows I’ve done on my own, there’s no one there to laugh at my jokes. Turns out I’m really boring.”

Fans can rest assured, then, that Dala will continue. Carabine hinted at more songs coming down the pipeline, though a new Dala album may have to wait.

“I feel like we’ve both been pursuing things that fulfilled us individually, but interestingly enough when we come back together onstage as Dala, I feel like we’ve never been more in sync with each other,” Carabine said. “I think we appreciate it more. Maybe having pursued other things, we realize just how lucky we are to be friends and to get along so well after 12 years of touring. We’re in a really good head space together.”

— Reporter: 541-617-7814, bmcelhiney@bendbulletin.com