Although the track's international success is undeniable, "Wake Me Up" received mixed reviews after its American debut at the Ultra Music Festival in March. EDM fans were confused by rock and bluegrass musicians playing live on stage alongside the Swedish DJ and producer. Einziger was among the rockers taking part in the jam session, along with his fiancée — accomplished bluegrass violinist and banjo player Ann Marie Simpson — and fellow Incubus bandmates Ben Kenney (bass) and Jose Pasillas (drums). Bluegrass big Dan Tyminski, old-school country crossover star Mac Davis and folk-rocker Audra Mae also took part in Avicii's Ultra performance.

Meanwhile, Incubus fans immediately took to social media to try to wrap their heads around the pairing of a rock guitarist and bluegrass musicians with one of the biggest faces among the new crop of EDM stars.

Despite the reaction, "Wake Me Up" became the first single from Avicii's upcoming debut studio album, #TRUE, out September 27 on PDRM/Island Records. The Mumford-lets-the-bass-drop song is now on track to become the fastest-selling U.K. single of 2013 so far. Released stateside June 25, it's gaining at American radio and expected to creep up the Hot 100 chart, this week at No. 68 (up from No. 81 last week).

"It doesn't matter how many times you write a song, for people to respond to it in such a drastic way is never expected," Einziger said in an exclusive interview with Radio.com this week. "It's never expected in Incubus, and it was not expected with this collaboration with Avicii and Aloe [Blacc, whose vocals are featured]."

Speaking of the seemingly odd pairing, Einziger said: "Over the last six or eight months that Incubus has been on hiatus, I've been writing lots of music with lots of different people, the connection that Avicii and I have with each other was unexpected. I think it was surprising to a lot of people that know me and also know him. We seem to operate in what seems to be different musical universes but when we got together the way that we started writing together, it couldn't have been more organic and effortless."