Two months ago Low ended their set at Chicago's Pitchfork Festival by pulling out a very unexpected cover of Rihanna's Top 40 ballad "Stay." The impact of the song was immediate—the crowd quieted down to a murmur and pressed in close, trying to place the melody and steep in its beautiful, aching melancholy. It ended up being one of my favorite moments of the weekend, even compared to powerful festival acts like Savages and Bjork, and I've found myself scanning the radio dial ever since, eager to hear another rendition of the song.

But not even Rihanna's own rendering has been able to sate me, and I've found myself wondering again and again just what it was about Low's cover of the song that was so unique, and so moving. Bands cover pop songs all the time; indie rock bands covering Top 40 R&B and rap songs is practically a cliché at this point. So what set this one apart, and why couldn't I wait to hear it again?

Well, thankfully I'm getting some answers today. The band just released a studio version of their cover of "Stay," recorded at the gorgeous Sacred Heart studio up in Duluth, and it's streaming on YouTube and available on iTunes, with proceeds going toward music education charity Rock for Kids.

As far as I can tell, there are a few things that really set Low's cover apart:

1. It's actually a great pop song

I think there is a tendency in the "indie" world (interpret that as you wish) to write off anything and everything associated with the mainstream. Somewhere along the way we were taught that if something is popular, it must be terrible, but that mindset can be really limiting, from a listening standpoint. Because, you know what? People pay lots and lots of money to have gifted songwriters write beautiful, yet simple pop melodies that will appeal to the masses. Sometimes, these melodies are so catchy they become grating. But at other times, they can take on more subtle nuances.

"Stay" is a beautiful song with a surprisingly complex melody. It was co-written by Mikky Ekko, who sings the male part on Rihanna's version, and pop balladeer Justin Parker, who helped Lana del Ray write her hit "Video Games." Much like "Video Games," the piano part is simple and somber, setting the stage for the tortured back and forth exchange between two voices.

2. They didn't ruin it with irony

So many indie covers of pop songs end up mired in layers upon layers of isn't it quirky we're doing this right now?-style irony. But there is no smirking happening when Low sing "Stay," which makes the cover even more risky. They're going "all in," so to speak, owning up to the fact that they sincerely love this Rihanna tune and that it spoke to them on a deep enough level that they wanted to reimagine it as their own song.

"Mim made it clear this morning that this Rihanna song 'Stay' is awesome," Alan Sparhawk tweeted a few days before covering it live for the the first time.

3. It speaks to who they are as people, and as a band

If there's one thing lacking from Rihanna's version, it's that no one actually believes that she'd ever be singing a song like this to a guy like Mikky Ekko; everyone knows she's probably referring to her relationship with Chris Brown, which makes it jarring with another, unfamiliar male voice enters. Sparhawk and his wife Mimi Parker have the advantage of actually being married to one another and experiencing all of the ups and downs inherent in that kind of long-term commitment. When Parker sings "Not really sure how to live without you," she means it. And when Sparhawk sings "Round and around we go," he's thinking about something deeper than some on-again, off-again fling. Their delivery actually reminds me a lot of the Parker-led song "Holy Ghost," when she sings "I can tell when something's wrong, and something's wrong." These are two voices who know each other better than anyone else knows them, and it gives the song an added element of realism and heft.

Beyond that, it's simply a great song for Low to play. They've taken a much more piano-driven approach with their last record, The Invisible Way, and Steve Garrington's keyboard playing ends up anchoring the song and connecting it to their other recent work in a way that seems very natural.

But you don't have to take my word for it. Listen for yourself, or grab it on iTunes to help Low support a great Chicago area music charity. The band's label, Sub Pop, also says that "Stay" is expected to have a wider digital release in the weeks to come.