WHAT makes a band change musical direction?

A clash of personalities, the departure of personnel, a hunger for commercial success? Or are the reasons more positive: a desire to experiment, growing confidence as writers across the ensemble, a belief that commercial success shouldn't matter that much anyway?

In the case of Admiral Fallow, the second half of that equation is closer to the truth. But perhaps it could also be argued that the new musical style spread right across the Glasgow band's third album, Tiny Rewards, is fuelled by something else entirely: Kevin Brolly's chilli.

Brolly is Admiral Fallow's clarinettist and keyboards player. A graduate of the Royal Conservatoire of Scotland, his fleet fingers have recently taken flight on King Creosote's From Scotland With Love album, and you might also find him behind the bar at Moskito, where he earns a living between band commitments.

But on the night I catch up with Admiral Fallow in the back of that very same Bath Street bar, Kevin Brolly is being crowned the chilli king of Glasgow. Even as we sit around a table talking through the artistic decisions that led to Tiny Rewards, "Brillzo's Chillzos" - a combination of beef mince, chorizo, onions, garlic, peppers and (hot, hot, hot) five different types of chilli - is winning Ad Lib's annual chilli competition on the other side of the city centre. I feel guilty that I've made him miss the judges' announcement in favour of a newspaper interview. (Time, then, for a commercial break: Brillzo's Chillzos will be found on the specials boards of Ad Lib's Ingram Street and Hope Street restaurants.)

What's this got to do with the album? Well, rewind to 2013. The five band members - Brolly, bass player Joe Rattray, drummer Philip Hague, flautist/vocalist Sarah Hayes and guitarist/lead singer Louis Abbott, multi-instrumentalists one and all - head off to a residential studio up near Fort William, not to record new material but to write, experiment with ideas and generally spend quality time together for four or five days. Over the next few months, they do this several more times.

"It was good to get away from Glasgow and be somewhere else where we could just hang out and chat and eat Kev's award-winning chilli," explains Rattray.

"I sometimes worry that it's me being a bit overbearing with the cooking thing," says Brolly. "But if they say they're happy for me to cook, then that's fine. I'm generally happiest when I'm cooking or baking.

"We were working all day, sometimes into the night," he continues, "but there were extended breaks when we just had dinner, got drunk, played board games, and it was nice just to hang out as pals as well as get some writing on the go."

"Because it was summer," Rattray resumes, "the weather was good and there were a couple of days when we went swimming. Loch Awe was just outside, and we swam in some of the rivers that fed into it, going around looking for waterfalls."

I get the feeling that this relaxed way of working, chilli included, helped the band reconnect with each other as friends and led to the more collaborative method of writing that underpins the new album. They have, after all, been together since meeting as music students in 2007, performing first as Brother Louis Collective then switching name to Admiral Fallow before 2010's debut, Boots Met My Face.

Last time I caught up with them, they were five months into the annus mirabilis of 2012, a year bookended by an appearance on BBC Scotland's Hogmanay television show in the early hours of January 1 and their first gig at the Barrowland Ballroom on December 8, with second album Tree Bursts In Snow appearing midway. A lot of touring was involved, a lot of festival appearances, enough to let them make a living as professional musicians albeit now with regular stints teaching or, in Rattray's case, working with promoters Synergy Concerts. ("It's useful to have someone in the band who can tell if we're being dealt with well by bookers and the industry," he admits.)

The first two albums saw them bracketed with Scotland's other indie-folk bands, but there was always something different about Admiral Fallow's sound. Yes, Louis Abbott could knock out a great pop tune with a rousing chorus - Squealing Pigs, Guest Of The Government, The Paper Trench - but elsewhere their training as music students would break through in little chamber arrangements, often featuring Hayes's flute and Brolly's clarinet.

Anyone who hasn't paid close attention to the band in the past 18 months will think there's quite a jump between Tree Bursts In Snow and Tiny Rewards. Their core fans, however, should be able to see something of a progression that carried through their one-off orchestral gig in Paisley Abbey with the RSNO in October 2013 ("My former piccolo teacher was playing," Hayes points out, "and a couple of friends that play with the RSNO are peers from college who either have a job in the orchestra or are on trial with them ... pretty scary") and the scores they composed for 10 short films that screened at the Glasgow Film Festival in March 2014.

However, Tiny Rewards should perhaps be seen, after Brother Louis Collective and the two albums, as Chapter 3 in the Admiral Fallow story. It's an album that demands more attention from the listener, as the shape and structure of each song isn't always evident from the get-go. There are wonderful melodies woven throughout, not just restricted to verses and choruses, plus brilliantly complex drum parts and a wider range of textures achieved through increased use of keyboards instead of guitars. A few bars of what sounds almost like a baroque keyboard sonata might drop in here (As Easy As Breathing), repeated bursts of a jazzy piano riff in there (Some Kind Of Life).

It's as if the individual personality of each band member has been allowed to flourish, even though the songs are being composed by the ensemble - and, indeed, that's pretty close to the truth.

"The way we previously worked, the material would often be from me, first and foremost," explains Abbott. "It would start with guitar, and maybe a verse and a chorus or perhaps even a fully formed song would be brought to the group, and we'd take it from there and arrange it as a band. This time, a lot of the music was written before there even were songs. Musical lines came to the fore a little more because there weren't words to steer clear of."

"Louis didn't have any songs hanging about, so it was a blank slate," Hague adds. "If anyone wanted to bring anything or play anything, that was totally cool. I would bring stuff on keyboards, show everyone and then it would get fleshed out on the other instruments."

"On the first two records, I was mainly playing clarinet and putting together melody lines to put over pre-existing songs and structures," says Brolly. "With this new record, because we had the time as well as more resources to get keyboards and synths, I was able to have a say in how the songs were going from an earlier stage. It felt good to be part of the bones of the songs rather than just being a cherry on the top."

"It's difficult to think of a word to describe the process," says Hayes, "because it's not the opposite of what has gone before, not two opposite ends of a spectrum. It's just a different way of working. I'd say 'collaborative'... but it's always been collaborative. Maybe just more collaborative. I would hope it's five musical identities working as one."

"'Democratic' is as good a word as any to describe how the songwriting is going," Brolly suggests. "Or certainly the music-writing, because Louis does still write all the lyrics, and I think that will always be the case for however long we're a band. That's the way he likes to work, and they're a bit more personal than the choruses or little melodies that the rest of us come up with. Not necessarily more important, but certainly more personal."

Abbott's lyrics were indeed personal on Boots Met My Face (the title comes from the song Subbuteo and concerns a nasty episode when he was beaten unconscious as a teenager) but they broadened out thematically on Tree Bursts In Snow. As the band members head into the upper end of their 20s, he's found more mature subjects for album three, such as the fact that rather a lot of his friends seem to be getting married and having children these days (listen to the superb second track Evangeline to discover how he feels about this).

"Whenever I'm writing a new lyric, the only challenge I set myself is not to write on a subject I've already written about," he insists. "This album is hopefully a bit more thought out and a bit more measured compared to the first two, in terms of the lyrical side of things."

And yet, he says, "doubt" is perhaps the key word that applies to Tiny Rewards. Doubt in that, although he knows his band mates are all excellent musicians, the new method of writing and working meant taking big risks.

"That is one of the themes that runs through it, this self-doubt thing, when you're trying something brand new. And that goes for me as well. In fact it's a theme that worked its way into quite a lot of the songs, really: not being sure if what we're doing is right or what we're doing is any good. That's not to say I didn't feel that for the songs from the previous two records, but I think when you're a bit younger, you're not really scared of anything, you just go for it. The older you get, the more you actually start to think about what you're doing, whether it's right or good."

Tiny Rewards is more than right, more than good. It's a brave move from a band who may only now be discovering their full potential. In a world where almost everyone tries to sound a bit like someone else in order to secure their market share, there is now probably no other band to which Admiral Fallow can easily be compared. And that's about as high a compliment as I can pay.

Tiny Rewards is released on the Nettwerk label on May 25. Admiral Fallow play Edinburgh's Hidden Doors festival on May 26, Mid Yell Hall and Mareel in Shetland on May 29 and 30, the Art School in Glasgow on June 10, Iona Village Hall Festival on July 3 and T in the Park on July 10