You never know what you've got until it's gone: a cliche in most cases, a truth in regard to Aereogramme.

The Glasgow quartet split in 2007, a few months after the release of their fourth album, having banged their heads against the walls of an impassive music industry one time too many. Suddenly a certain, admittedly small, mostly male section of the listening public were left realising what had been lost.

Thankfully, when half of the band – singer/guitarist Craig B and guitarist/programmer Iain Cook – re-emerged in the fresh form of The Unwinding Hours, they also realised what had been found: a new band with roots in Aereogramme's gorgeous melodies and emotionally powerful rock arrangements, but with a distinctive, less sonically extreme impact of its own. "There was an exquisite grace amid [Aereogramme's] punishing noise, and it's this that characterises The Unwinding Hours: a yearning, burning, wide-eyed romanticism," wrote Simon Stuart in the Sunday Herald when their self-titled debut was released two years ago. "These 10 beautiful songs are, quite simply, a testament to the power of music. They are informed by the duo's noble history but are the beginning of a new chapter."

Chapter two of The Unwinding Hours' story is unfolding when I meet Craig and Iain on a scorching afternoon in the west end of Glasgow. It's only days before their second album, Afterlives, will become available, again on the Chemikal Underground label, but despite the rave review that tumbles from my lips – Afterlives is a more instantly accessible, more openly euphoric successor to what was my album of the year back in 2010 – the pair remain realistic about its prospects and the slow progress of the band itself.

"Personally I feel comfortable with the way that we do things," admits Craig. "We had put all our time, effort, energy and thought processes into trying to make a living from Aereogramme. And then it became a grind, so that type of pursuit is not something that I'm interested in.

"I'm 100% confident of the record that we've made. It'll find its own audience, and it's quite nice to just let it go. I don't feel like we've put any less work into this music, but I realise now that I'm far less frustrated by the outcome. The outcome will be what it will be, and it doesn't change how proud I am of the album and all the people involved. Creatively, it's incredibly fulfilling. I feel liberated by it."

It's certainly to Chemikal Underground's credit that, in this belt-tightened day and age, Craig and Iain feel no pressure from their label. They write, record and, when enough songs are ready, deliver an album and play a few gigs.

Having learned lessons from those Aereogramme days, they don't consider The Unwinding Hours a full-time occupation (Iain, for example, is also a member of recently launched buzz band Churches and produced Karine Polwart's excellent new album, Traces). "Again, the expectations are very realistic about what that is," adds Craig, "about being smart about what you do and not burning out."

The big hypothetical question, of course, is this: is Afterlives what a sixth Aereogramme album would have sounded like?

"It feels like a completely different project," insists Iain. "There was so much discussion around the time of [final album] My Heart Has A Wish That You Would Not Go that we were going to do two albums: one would be extreme and heavy and guttural and dark, the other a lot sweeter, sadder, more expansive, for want of a better word. But I don't know. That was a band in the way that this doesn't feel like a band. This feels more like a studio project that we are able to realise live."

"I understand why there was a glass ceiling for Aereogramme, because it was aggressive and the extremes were very extreme," continues Craig. "When we went heavy, it was as heavy as we could go, and when it was sad, it was really sad ... Before, like a younger person, you'd be shouting at the sky. As you get older, you realise you can still be as angry and concerned about certain things, but you focus and control it a lot more. To me, The Unwinding Hours is far more about being able to control that – caging the beast."

Craig has always wrapped that anger in the most beautiful melodies, and Afterlives contains some of the most affecting he has ever written. It's not something he imagines letting go of.

"Yeah, I can't stand music that doesn't have melody," he agrees. "I don't understand music without that hook. Melody comes from the influence of my father's record collection: Michael Jackson, Billy Joel ... A wee while ago I was going through my own record collection, all these post-rock records from when I was obsessed by Tortoise and their offshoots. And it suddenly dawned on me that, on my deathbed, I'm not really going to be crying out for that Gastr del Sol B-side remix. I'm going to be wanting AC/DC, I'm going to be wanting Abba, I'm going to be wanting all these amazing melodies."

Whoever makes that playlist should make sure to leave space for The Unwinding Hours to be on it too.

Afterlives is released tomorrow. The Unwinding Hours play The Tunnels, Aberdeen, on August 31 and Stereo, Glasgow, on September 1