In 1997, Rainer Maria was a sinewy new post-punk trio from Madison, Wis.

It had an arty but melodic sound and two lead singers in bassist Caithlin De Marrais and guitarist Kyle Fischer. It had a lauded and loved debut album out on independent label Polyvinyl Records, and charter membership in a Midwestern scene that was at the moment defining both late-'90s indie-rock hip (Joan of Arc, Braid) and an emergent under-the-radar subgenre called "emo."

Due to De Marrais and Fischer's literate, impressionistic and symbol-laden lyrical bent — and also in no small part to the group's being named after an early 20th-century German bard — the adjective most often used to describe Rainer Maria was "poetic."

"Maybe for a split second I thought, 'jeez we're irrelevant, just like poetry is irrelevant,' but the next second I was just, 'oh, whatever,'" De Marrais remembers thinking of the ubiquitous qualifier. "I'm not gonna succumb to whatever pop culture is casting off at this point."

In 2006, Rainer Maria is a dynamic, inventive and infectious pop-rock trio from Brooklyn. It has a slightly arty and wholly melodic sound, and one lead singer in De Marrais. It has five full-lengths under its belt, the latest of which, this year's nearly flawless Catastrophe Keeps Us Together, was the first album to be released by Grunion Records, a new label founded by wildly successful artist managers/industry types Cliff Burnstein and Peter Mensch.

And if Rainer Maria was ever "emo " — which it wasn't, really — its current, creatively anthemic style bears exactly zero resemblance to today's commodified blend of loud guitars and teen angst.

"[The tag] certainly has followed us, and I never have applied that to us, aside from sort of being in the similar peer group — Joan of Arc, The Promise Ring; when those bands were being called that, I was perfectly happy to be identified with that scene," says De Marrais. "The name doesn't resonate with me very much, particularly now, with it being mainstream and having this very specific looking and sounding music. I've always considered us more indie rock, I guess."

Yup, a lot has changed in nine years. While Rainer Maria's status as an independent act on the cusp of a wider breakthrough has remained fairly constant — the band always does exceedingly well with critics and at college radio, and each new album demands an obligatory Next Big Thing-style feature in the glossy magazines — its sound has most definitely not. The combo's rougher, basement-show-bred characteristics have been smoothed out over time, its fractured, vaguely post-hardcore-friendly dabbling gradually overtaken by brighter and more polished songwriting that revels more often in traditional pop and rock hallmarks.

For most longtime fans, the biggest and most obvious shift in the band's style came with '03's Long Knives Drawn, the first CD to feature De Marrais as sole vocalist (freeing Fischer to concentrate on guitar). Catastrophe Keeps Us Together continues that trend; De Marrais chalks up the change to natural growth and an interest in keeping things fresh rather than any plotted career trajectory and hints that the format could change back, or change again, at any time.

"It's become something that we feel works at this point," she says. "There's no final law passed on the subject, and we might experiment in the future — to be honest, we've been taking a crack at some new songs recently. I just mean to say that it's all an experiment, really.

"As long as we're enjoying it and having fun with the songs we're writing, it's not really an issue. Being together for so long, we have the chance to explore different ideas and tracks and instruments and voices and stuff."

The absence of Fischer's vocals certainly hasn't hurt the music in any substantial sense. His guitar work fills the one-time spaces between De Marrais' bass and drummer William Kuehn's rhythmic anchor with tasty texture, building figures that appear fragile, yet more than bear the weight of the songs. And De Marrais' voice has attained a confidence never before heard. Her choice of melody is increasingly better suited to the music as well. She's moved away from writing her lyrics first, and now lets the instrumental arrangements inspire the words.

"Now, I really listen to the songs we're writing first," she says. "I have many [lyrical] ideas already in the back of my head, but I don't want to go into a song before I get a feeling of what the song already sounds like to me, I guess. I think it's nice to work that way, it feels natural. It feels better, for me anyway, than having a long list of lyrics I have to fit into music. I think I may have been getting a little wordy at times [in the past]. But I kind of like holding the words out longer, instead of trying to cram it all in."

As much as Rainer Maria has changed, some things haven't. The band still adheres as much as possible to the punk-scene do-it-yourself philosophy, preferring its perennial fringe position to compromise in the hope of bigger returns. De Marrais, Fischer and Kuehn still make music on their own terms; the results may be a little catchier than in the past, but De Marrais says the process is still all about satisfying the band members' personal expectations.

"We're aware that there are people, fans, that prefer the older albums for various reasons," says the bassist/singer. "Like Kyle's singing, which is a perfect reason, he's a great singer. What we're trying to do is just write better songs. We are our only critics, the only people we have in mind when we write."

And the result can still be very "poetic."

"Poetry is a thing I still discover daily," De Marrais says. "What people say about us is less important to me than what I'm writing. The work feels more important to me."