Toronto-based folk musicians the Great Lake Swimmers. From left, Greg Millson, Erik Arnesen, Tony Dekker, Darcy Yates and Julie Fader. The band has just released their fourth album, Lost Channels. (Ilia Horburgh/Weewerk)

Toronto's Great Lake Swimmers make music that leaves you feeling as though you've been let in on a tender, precious secret. Their songs are hushed affairs that unfold with delicate acoustic guitars, sighing pedal steel and feathery percussion, all anchored by singer-songwriter Tony Dekker, who conveys his intimate revelations in a pure, airy tenor.

Great Lake Swimmers are known for recording in unconventional spaces: a grain silo, a heritage building and, most recently, an island castle.

So it was a bit of a shocker when platinum-selling crooner Josh Groban covered the band's song Changing Colours — a dreamy track off their 2007 album Ongiara — at last year's big benefit bash Neil Young held for the Bridge School in California. As odd as it was to hear the adult contemporary balladeer's interpretation of Dekker's restrained melodies, it's even more baffling that Groban was familiar enough with this humble little Canadian band to perform one of its (lesser known) songs in concert.

"I'm still trying to figure it out, actually," Dekker chuckles during a recent phone interview. "I scratched my head and watched it on YouTube and thought, 'Well, uh, the gospel choir was a nice touch.'" If nothing else, the Groban incident is a shining example of how Dekker's songs can connect with the unlikeliest of people. In fact, that's how Great Lake Swimmers ended up decamping to the gorgeous Thousand Islands region (the network of islands stretching from south of Kingston, Ont., to New York State) to create the bulk of their latest album, Lost Channels.

Dekker and his band – which currently includes drummer Greg Millson, bassist Darcy Yates, banjo and guitar player Erik Arnesen and backing vocalist Julie Fader – are known for recording in unconventional spaces. Great Lake Swimmers took over an abandoned grain silo in rural Ontario for their 2003 self-titled debut; Ongiara was made in London, Ont.'s Aeolian Hall, a heritage building with great acoustics.

(Nettwerk Records)

While finding these spaces has often been serendipitous, the path that led the band to the Thousand Islands was more remarkable than usual. Dekker and his crew recorded a performance for Stuart McLean's CBC Radio show, Vinyl Cafe, on location in Gananoque, Ont. It caught the ear of Ian Coristine, a historian and photographer of the Thousand Islands, who fell in love with the Swimmers' music and issued an open invitation for the band to come hang out in the region.

"When it came time to record the album, we gave him a call," explains Dekker. "He started rhyming off a list of acoustically interesting places in the region. At one point, he mentioned that he knew some people who manage this castle on an island and asked if we'd be into recording there. I was like, 'Of course!'"

It's safe to say Lost Channels was profoundly shaped by the region. The title of the album comes from a part of the St. Lawrence Seaway where a boat mysteriously disappeared back in the 18th century. While Dekker says he'd already written most of the songs before he and his bandmates hauled their gear over to Singer Castle, he also acknowledges that he strove to "incorporate the mood and the imagery of the surroundings" into the recording process. The track Singer Castle Bells isn't really a song — rather, it documents the hourly chimes at the old manor. It's simple but hauntingly pretty.

There's a magical, warm quality to the songs on Lost Channels, a richness and collective spirit that hasn't always been present in Great Lake Swimmers' songs. The Swimmers' first two albums, while still lovely, often felt a bit too breakable, that the airy arrangements supporting Dekker's plaintive confessionals might dissolve if you listened too hard. The seeds for a rootsier sound were planted on Ongiara and now they've come into full bloom.

The delicately layered banjo plucking and resonant Hammond organs that surge on the jubilant chorus of Pulling On A Line draw you right into the room where the song was recorded. On Everything Is Moving So Fast, Serena Ryder harmonizes with Dekker, and their tones are so complementary, it's like they're two heads on the same beast.

Great Lake Swimmers in performance. (Weewerk)

"I always thought one person worked better than having too many cooks in the kitchen," Dekker says, "but I've been listening to more bands like the Band – what a great chemistry that group of people share! More and more, I'm understanding what the interactions of a group of people bring to the table, and how that can be even more productive than just one person's undiluted opinions.

"The current [Great Lake Swimmers] lineup has a really great chemistry, which is something I'd like to work on more," he continues. "It's something I think will develop well over the course of this tour."

Extensive touring has served the Swimmers well. Last summer, Dekker and company opened for Alison Krauss and Robert Plant when the Grammy prom king and queen headlined a packed show at Toronto's Molson Amphitheatre. Considering Great Lake Swimmers have more experience playing cozy churches and quiet folk clubs than cavernous stadiums, one assumes the transition to a stage of that magnitude must have been daunting.

Nah, says Dekker.

"I think we all realized that we'd been touring for so many years that we sounded — well, let's say I found that I was not nearly as nervous or as reluctant to step on to that stage as I thought I'd be. It was a really amazing experience, actually.

"And having a chance to meet Robert Plant and Alison Krauss, who are both heavyweights in their respective fields, and have created this amazing collaboration, it was a really great moment for the band," says Dekker. "I love that classic bluegrass-slash-blues-slash rockabilly thing they've got going on. Robert Plant watched our set from the side of the stage and gave us the thumbs up. That was … Man, I don't know what the word is! It was just a really great moment."

Lost Channels is in stores now.

Sarah Liss writes about the arts for CBCNews.ca.