At Deer Lake Park on Monday, May 27

Despite all indicators pointing toward a biblical downpour for Sigur Rós's performance at Deer Lake, there was only the slightest hint of drizzle when the Icelandic band took to the stage at the Burnaby park. Or at least I assume that was the case; thanks to the absolute shit show that is parking at Deer Lake, the show was already under way when I arrived.

I came at an opportune time, however: Georg Hólm had just begun the slowly circling bass line that serves as the pulse of "Ný batterí". That song, from Sigur Rós's breakthrough second album, 1999's Ágætis byrjun, typifies one of the group's primary songwriting tricks—slow, meditative verses that arc into blaring, melodramatic choruses, with frontman Jónsi Birgisson sawing away at his Les Paul copy with a cello bow and sending peals of droning noise up into the darkening sky. It might be a formula, but it's an effective one, especially in a live setting.

For its next trick, however, Sigur Rós proved that sometimes the fireworks aren't necessary. "Untitled #1 (Vaka)" is a piano-driven slow-burner that never reaches for the heavens, nor does it have to. Its beauty lies in its unassuming quietness, and the sense that Jónsi is revealing some long-held secret, even if none of us will ever know exactly what that is. (The song, like the rest of 2002's ( ) album, has lyrics in Hopelandic, a gibberish language of Jónsi's own devising.)

The guitar-bowing was at its most stratospheric on "Svefn-g-englar", the 10-minute masterpiece, also from Ágætis byrjun, that brought the Reykjavík band to the world's attention. To an impossibly sedate tempo—it would be downright plodding if so much weren't happening overtop of it—Jónsi drew the bow across the bridge of his guitar, sometimes softly and sometimes attacking the damn thing in a way that yielded an air-splitting groan, as if the whole planet was settling like an old house.

A publicist for a label that I won't name (because he might be embarrassed, as he should be) once informed me that he couldn't stand Sigur Rós because of what he called the Céline Dion moments. He meant that point in many of the group's songs where (with the help, on this occasion, of string and brass sections) they explode into an operatic crescendo of sound and fury. Well, maybe fury isn't quite the right emotion. But on a song like "Varúð", the point of those Titanic moments becomes obvious: when they hit, you feel...something. At a Dion concert, you know exactly which heartstrings she's tugging at, because the songs are so obvious and the manipulation of the audience so transparent. Whether it's because Jónsi sings in Icelandic (and occasionally the aforementioned Hopelandic) or because the group's compositions aren't intended to convey anything that can be parsed as readily as "My Heart Will Go On", the feelings stirred by Sigur Rós are ineffable.

It may be trite to say that a song like the new "Hrafntinna" expresses the otherwise inexpressible, but seeing as how I find myself genuinely moved by the so-called "Céline Dion moments", I may be guilty of basking in triteness.

In any case, there's very little basis for comparison between Quebec's most famous daughter and the band that made the forthcoming Kveikur. On the new record, the often-ethereal Sigur Rós bares its teeth, showcasing an aggressive side that, until now, we've only seen in brief glimpses. Numbers like the title track and the epic-length "Brennisteinn" crackle and throb with near-industrial intensity, and their bass-heavy grooves might even owe a debt to the darkest strains of dubstep. Just how heavy is the new stuff? Well, one dude near the front of the stage, clad in a denim jacket with the sleeves hacked off and a Black Sabbath patch on the back, responded to it by whipping his hair back and forth like Jason Newsted in the headbanging glory days.

By coincidence (or maybe not), the harder Sigur Rós played, the harder the rain fell. And, as if to prove that it has always been capable of rocking out, the band reached back to ( ) to close the concert with "Untitled #8 (Popplagið)", stretching the song's towering-inferno coda up to the 15-minute mark, with everyone on-stage contributing to the sweet, sweet rising chaos. Drummer Orri Páll Dýrason pounded at his kit as if it was possessed and he were the exorcist; touring guitarist Kjartan Dagur Hólm brought the shoegazing noise; and Jónsi hunched over his guitar, swinging it around and toppling lights and his own microphone stand. It was thrilling, cathartic, and heavier than fuck.

Let's see Céline Dion pull that off.