The general consensus is that Eternal Summers has taken a huge artistic step forward with its second album, the critically lauded Correct Behavior. Reached in the tour van on an Indiana highway, singer-guitarist Nicole Yun acknowledges that, for a whole host of reasons, the record is a big departure from the band’s ultra–lo-fi, minimalist-minded debut, Silver.

Determined to move forward this time out, the Roanoke, Virginia–based band decided to add another body to the mix. The original lineup of Yun and drummer Daniel Cundiff expanded to a trio, with bassist Jonathan Woods joining the fold. During the writing process, Eternal Summers’ frontwoman made a concerted effort to unleash her inner guitar hero, asking herself questions like “What would Billy Corgan do?” That would prove more challenging than it looks on paper; because she grew up playing piano and a bit of cello, Yun doesn’t exactly consider herself a six-string virtuoso. This makes her napalm-powered performance on Correct Behavior cannonballs like “You Kill” all the more impressive.

“When we started the band, it was actually never really serious,” Yun says. “Mostly, we viewed it as a project for becoming better at our instruments, and becoming better at writing songs. I’m not a trained guitarist, and Daniel isn’t a trained drummer. So for this record, ‘You Kill’ ended up being a real jumping-off point. It was like, ‘We’re going to try to execute all the things that we want to do well, even if we can’t totally pull it off yet.’ That really helped us reach another level.”

Having a major impact on Correct Behavior was their acceptance that, sometimes, an outside set of ears can do wonders for a group looking to reinvent itself. After pushing themselves out of their comfort zones as songwriters, Yun and Cundiff decided to abandon the DIY route they’d embraced since forming in 2008. Instead, they sent a batch of self-recorded songs to Raveonettes singer-guitarist Sune Rose Wagner, a proclaimed fan of the group. Working with fellow producer Alonso Vargas, Wagner got busy sculpting the songs.

“We are from a very insular music scene, where we’ve prided ourselves on a real DIY lifestyle,” Yun says. “We’ve always had our friends record everything, and we’d do everything all analogue. After years of doing that, working with anybody was a huge step. Sune and Alonso pulled all sorts of things out of our music—they had a really interesting way of looking at the raw material, but still being really sensitive towards it. Take the song ‘Summerset’, for instance: that was the least formed of the songs we sent Sune. He turned up the chorus effects on the guitar—like, turned it up a lot, giving it a Cocteau Twins vibe. Everything became somehow more epic-sounding.”

Correct Behavior is indeed epic-sounding, from the sparks-shooting guitar on “Millions” to the searing feedback flares on the aforementioned “You Kill”. Obviously determined to mix things up, Eternal Summers is more ’80s than John Hughes directing Molly Ringwald in a Psychedelic Furs video in the marvellously morose “Girls in the City”, while “Good as You” plays connect-the-dots between ’60s folk and class-of-’92 alternative rock.

Yun describes the whole Correct Behavior experience as nothing less than life-changing, suggesting that, having taken its big step forward, the group won’t be revisiting its lo-fi roots anytime soon.

“We explored everything we could as a two-piece,” she says. “We did everything we could without bringing in backing tracks and things like that. For a while we were thinking of going even quieter and sparser. That was a cool thought, but I like the way that we now have different tools to write different kinds of songs.”

Eternal Summers plays the Waldorf on Sunday (September 9).