For most, the name AFI has been more closely associated with the American Film Institute than with some eclectic San Francisco art-punk group.

Now, the fire is quickly spreading outside the indie community.

From the time they formed in 1991, AFI (which stands for A Fire Inside) have kept the flames burning within. Their songs simmered with haunting introspection and their music crackled with outsider energy that wasn't intended for mainstream ears. The band's last two records, Black Sails in the Sunset (1999) and The Art of Drowning (2000), sold more than 100,000 copies each — mostly through word of mouth — to a loyal alliance of iconoclasts.

But their fanbase seems to be growing. In its first week on the Billboard albums chart, AFI's new album, Sing the Sorrow, debuted at #5, selling in excess of 96,000 copies.

"It was really unexpected for us how much people got into it," said mascara-painted frontman Davey Havok. "We like all the songs, but we weren't really sure how many people would besides ourselves."

The swell of interest was triggered by the momentum of the single "Girl's Not Grey," which was introduced to rock radio about two months ago. The song churns in the verses and soars at the choruses, and though instantly accessible throughout, it's peppered with enough dissonant chords and weird textures to remain compelling to those that like their rock quirky.

David Slade, who has also worked with P.O.D. and Stone Temple Pilots, shot a performance-based video for the song.

One reason AFI have been able to connect with a mass market is because their songs appeal to a variety of audiences including punks, goths, metalheads and alt-rockers.

"We didn't make any conscious effort to fit in with anything," explained guitarist Jade Puget, who writes most of the band's music. "The kids who come to our shows are an assembly of the different parts of all these different scenes, which is very cool."

Still, A Fire Inside aren't exactly a marketing director's dream. The bandmembers collectively look like a cross between '80s goths and swing musicians, and many of their songs demand repeat listening before they sink in. Also, it can be pretty challenging to decode Havok's dark, ultra-cryptic lyrics.

"I heard a DJ say the other day, 'If anyone could call in and tell me what ['Girl's Not Grey'] is about, please do,' " laughed Havok, who refuses to fully reveal the mystery. "The song is based on detachment, seclusion and separation, but I intentionally don't write in a way that is very specific so that people can take what they need to from my songs. When I was growing up there were songs that meant a lot to me, and then I found out they meant something entirely different to the artist, and it ruined it for me. I never want to do that to someone."

Perhaps the main reason AFI have suddenly connected with former non-believers is revealed in the songwriting on Sing the Sorrow. With the help of veteran producers Butch Vig (Nirvana, Garbage) and Jerry Finn (Green Day, Blink-182), the group has crafted tunes rich in dynamics and textural flourishes (haunting sounds, unexpected techno beats), but structurally pure and far more melodic than the group's past offerings.

"There's a progression most songwriters go through," Puget said. "It's really easy to write a fast, heavy song, and it's far harder to write a melodic, slow song. It's also far more interesting because the intricacies of putting together chord progressions that can actually portray an emotion are far more difficult than putting together something and just screaming over it. So that's what we did because we always want to challenge ourselves."

When any band with a niche audience strives to develop, some old-school fans inevitably cry "sellout." So naturally AFI's evolution from Offspring-influenced rockers to more commercial songsmiths has left some former devotees fuming inside. Havok remains unconcerned.

"We don't have to worry about betraying any scene because we really didn't come from one," he said. "Anyone who's been with us for the past four releases would find no shock in this record. We really don't fit into any genre, so as far as anyone saying, 'Oh, you aren't punk rock anymore,' well, you obviously haven't been listening to us for the past eight years because we haven't been [strictly] punk rock in that long."