Call it the Animal Collective Effect. A lot of introspective avant-garde rock bands are courting exuberant pop these days. Take a look at Sigur Ros’s most recent album. It’s upbeat and catchy. Who would have expected such a serious, moody band to put out something so fun?

It appears that fellow Icelanders Múm have taken a similar turn recently. Their old stuff was mostly instrumental, childlike electro-pop, so typical of the indie-sphere at the turn of the century. Múm did it better than just about anyone though, so I was a little disappointed to hear throughout the course of many indifferent album reviews that they hadn’t retained that sound over the past decade. It’s not an exaggeration to claim that 2009’s Múm is virtually a different band. However, the new stuff is great too, if keeping in step with the kind of ebullient neo-folk popularized by bands like Animal Collective, the Dodos and Dan Deacon.

Many unexpected influences are now evident in Múm’s music. “If I Were a Fish” sounds like it could even be a country song, steel guitar and all. I also hear hints of Eastern folk, Spaghetti Western, and even Latin dance. The biggest change is the forceful delivery. They haven’t exactly gone hardcore, but the music is notably more upbeat than on previous albums. It’s impossible to watch Múm perform without a dumb smile on your face. They’re all about death lately, with one song proclaiming, “We’re going to die like little flies.” But they’re OK with that. “The Smell of Today is Sweet Like Breastmilk in the Wind” is straight up dance punk, ending with everyone, audience included, shouting, “We’re not afraid to die!”

Finally, sweet relief came with the song we’d all been waiting for, “Green Grass of Tunnel”, rendered with triumphant cries to an overjoyed audience. This sensitive indie anthem is right up there with “Aeroplane Over the Sea” and “Autumn Sweater” as far as I’m concerned, not to mention a significant touchstone for Gen-Y music geeks like myself who were just dipping their toes into what came to be known as post-rock when the song hit Kazaa, I mean, college radio. It’s nice to see the band evolving into something new without losing any charm, but I would have hated to leave the venue without hearing the song, even this upbeat version.

The band is adorable. The two girls that provide much of the lead vocals also play violin, guitar, and other toy instruments. (Speaking of toy instruments, what is it with Icelandic rock bands and the use of tiny pianos, kazoos, tinkling bells and miniature accordions? I’ve seen four or five bands from that mystical place, and all love to incorporate childlike sounds into their music with almost Seussian instrumentation). After each song they smile and blush and look at each other with nervous giggles. When they chant, “You are so beautiful to us / We want to keep you as our pets,” the audience replies, “No, you”, with their eyes. We could listen to them talk about marmalade ferns and soggy eyeballs all day with those super-cute accents. The six-piece gathered at the front of the stage after their last song. Clasping their hands together as in prayer, they bowed their heads slightly like monks from some fantasy religion.