In The Tain, an Irish legend that the Decemberists set to music for a 2004 EP, a supernatural figure turns herself into an eel, a wolf, and finally a heifer in order to stymie the plans of the human warrior who earlier rejected her offers of love. For their 2006 breakthrough LP, The Crane Wife, the Portland band drew on an ancient Japanese tale about the doomed marriage between a shape-shifting bird and a humble peasant farmer. And in their latest effort, The Hazards of Love, Colin Meloy and company have crafted a song cycle that opens with a young woman named Margaret finding and nursing an injured fawn, which then turns into the young man of her dreams.

Armed with approximately two semesters’ worth of psychological training, I’m willing to speculate that Meloy’s apparent obsession with strange transformations relates to his mixed feelings about becoming an indie-rock icon. This theory is reinforced by the fact that, on The Hazards of Love, Meloy plays two distinct roles: the sweet young man (and erstwhile fawn) William, and a sinister, infanticidal psycho known only as the Rake. A more provocative metaphor for Meloy’s bipolar existence—centre of attention on-stage, bookish recluse off—would be hard to imagine, but that’s not something Decemberists drummer John Moen really wants to comment on.

“We’re used to assuming that songwriting is a real personal thing, or that you’re probably trying to say something about yourself when you write a song, even if the characters have different names,” Moen admits, reached on his cellphone while running errands near his Oregon home. “But I’m hesitant to go there, for obvious reasons. I listen to him [Meloy] do interviews, and we talk about what things mean, and I think he just has a real interest in stories.

“He wouldn’t mind me saying that he’s a bit of an introvert,” the drummer adds. “He spent a lot of his childhood with books, and he’s just interested in recurring themes in folk stories. That was kind of the impetus for this record. He’d been listening to a ton of British folk music and noticed that the character of Margaret kept coming up, and shape-shifting beasts kept recurring from song to song. So I think he just picked all his favourite motifs and wanted to see what would happen if they kind of got thrown together in a stew.”

The result is the Decemberists’ most ambitious record to date, both sonically and conceptually, something that’s forced the band to radically up its game. To bring The Hazards of Love to the stage, the quintet has added two female singers: Becky Stark, playing Margaret, and Shara Worden, in the role of William’s adoptive mother, an evil forest queen. For the first time, the group is touring with a custom-designed light show, and the players are also having to stretch their abilities to cope with the demands of a score that ranges from lighter-than-air balladry to industrial-strength crunch.

Another of Meloy’s obsessions is the intersection between English electric folk and hard rock—think Jethro Tull, or Fairport Convention singer Sandy Denny’s guest turn with Led Zeppelin on “The Battle of Evermore”—and on The Hazards of Love, this shows.

“It’s just the most fun I’ve had being on tour,” says Moen of playing the new disc on-stage in its entirety. “I’ve been doing this a long, long time, but this is definitely my favourite Decemberist activity. It’s fantastic—playing hand drums here and shakers there, and then feeling like a rocker when you get into some of the riff rock that’s on the record, which is as heavy as you want it to be. I love it.”

One question still remains, though. Is The Hazards of Love a rock opera? Meloy says no, but some of the other Decemberists aren’t so sure.

“We were being interviewed in New York recently,” Moen recalls. “Becky was at the microphone, and so was Colin, and the interviewer was saying, ”˜What about this rock opera, Colin?’ He was kind of saying, ”˜Well, it’s not really,’ and then Becky, out of nowhere, went, ”˜Christ, I don’t see why you don’t just call it a rock opera.’ It was like a band tiff in front of a live studio audience—microphones on and everything. We survived just fine, but we’re not even all that sure what it is, sometimes.”

Song cycle, rock opera, quasi-theatrical project: The Hazards of Love is all of these, but most importantly it’s an undeniably gorgeous undertaking by a band that seems determined to stretch the boundaries of popular music. And if that makes the shy and soft-spoken Meloy a star, so be it.

The Decemberists play the Vogue Theatre on Tuesday and Wednesday (July 21 and 22).