NEW YORK -- Even though Train is responsible for the ditty that by some measures was last year's most popular song -- the ubiquitous "Hey, Soul Sister" -- the trio has yet to experience that kind of massive mainstream popularity. Although Pat Monahan has fronted the group for over a decade, he's never been a household name, and people who know the chorus of "Soul Sister" probably wouldn't be able to name Train's other two members, guitarist Jimmy Stafford and drummer Scott Underwood.

Monahan acknowledges that kind of anonymous success used to grate on him -- but he puts the emphasis on "used to."

"Being under the radar as a celebrity isn't the worst thing that can happen to you. I think that maybe that's the reason for the longevity," says Monahan.

"For a long time I was disappointed about it. It was like, 'How come I can't get on Us Weekly, how come we're not on the cover of Rolling Stone? What did we do wrong?' But now I think that we just don't care like that. That's not why we started this. ... So we're learning how to have a lot of fun with it and keeping in mind that thinking about celebrity is thinking about the wrong thing. Thinking about the music is thinking about the future."

Keeping the focus on music has led to a rebirth for Train. The group is nominated for a Grammy Award for best pop performance by a duo or group with vocals next month for a live version of "Hey, Soul Sister," which is still No. 1 on the adult contemporary chart a year after its release. While it never reached that spot on the overall pop chart, the song permeated pop culture and showed its dominance in other ways: It was featured on "CSI: New York," in Samsung commercials, was the most downloaded song on iTunes in 2010, and has been certified quadruple platinum.

"Even in other countries where they don't speak English, that song has been very successful," said Stafford. "I attribute it to the melody, some really catchy hooks ... the ukulele is [also] a really unique sound that people just seem to be drawn to that."

The notion that they'd have one of the biggest-selling songs of any year was doubtful a few years ago. Monahan, Stafford and Underwood, founding members of the band (it started out as a quartet), decided to part ways after a tour that saw Train starting to unravel. The band was coming off an album, 2006's "For Me, It's You," that didn't garner the sales or the hits of their previous records, the 2003 gold-selling "My Private Nation," which featured the hit "Calling All Angels"; 2001's double-platinum breakthrough CD, "Drops of Jupiter," which included the Grammy-winning song "Drops of Jupiter (Tell Me)"; or their 1998 platinum self-titled debut.

"It was really clear to us. We were not getting along and we were not enjoying the process. ... We just knew," Underwood says of the decision to take a break. "It was a really scary choice to make because it was kind of a leap of faith that we would ever get back together again. Also, taking time off in the music business, it's a very fickle audience. We didn't know if anyone would ever want to listen to our music again."