As announcements go, it wasn’t exactly an ‘LSO gets Simon Rattle’. When B Tommy Andersson was unveiled as the new Composer-in-Association at the BBC National Orchestra of Wales last summer, not many people outside Scandinavia had much idea who he was.

The temptation at this point is to write that ‘everything has changed’ since then: that a series of concerts from Wales’s national symphony orchestra has made Andersson an unlikely hero in the land of song, the good folk of Cardiff whistling his tunes as they amble down Westgate Street. True: the St David’s Hall punters made their (positive) feelings about Andersson’s music known after the orchestra introduced them to it back in October with a colourful performance of his signature piece, The Garden of Delights. But the reality is rather more subtle. And a bit more meaningful.

On September 3, the BBC National Orchestra of Wales will give the world premiere of Andersson’s new orchestral work Pan at the Proms, the first he’s expressly written for its players. But for all the symbolism of Wales’s national orchestra playing a work by its Swedish discovery on a world stage, there were more salient lessons to learn about Andersson’s time with the ensemble at a distinctly lower-key concert back in February.

This was, in a sense, the apex of the BBC NOW’s year with the composer (and it very much was a year ‘with’ him). At a public studio concert in Hoddinott Hall, the BBC NOW played an entire programme of Andersson’s music under Principal Conductor Thomas Søndergård. Before the performance a modest crowd had congealed into a bottleneck by the entrance to the auditorium, a good proportion of which were students. In the middle of that gaggle of youths stood Andersson himself, animatedly imparting technical details about the works that were about to be performed. Not because he’d chosen to, but because he’d been asked.

And it was probably a two-way conversational street. As part of Composition Wales 2015, Andersson has perused dozens of scores from young composers in Wales in preparation for workshops with their creators and, for a lucky few, full renderings of their works with the orchestra. ‘Actually I’m particularly thrilled about that opportunity’ says Andersson when we meet on the afternoon of that February concert. ‘The only way to improve as a composer is to hear what you have written and actually see people attempting to play it; that is something I remember well.’

More significant than that detail, though, is the overarching concept. Getting a composer embedded in an orchestra is one thing; having him extend his involvement to that orchestra’s associated partners – indeed, embedding him into the ‘new music’ life of an entire country, as is only possible in a country of Wales’s modest proportions – is quite another. It’s also a clear indication of how the idea of a composer-in-association/residence has developed from the rather moribund model of a man turning up to hear his works performed, taking the applause, then leaving again (and not just at the BBC NOW: note the BBC Philharmonic’s plans for its own composer-in-association, local lad Mark Simpson).

‘It’s our dual role as a national and a broadcasting orchestra that has been partly responsible for that [change]’, says Michael Garvey, director of the BBC NOW. ‘It’s given us the chance to make much more of Tommy’s presence and to use him to grow our work with the Royal Welsh College of Music and Drama.’ For Andersson himself, involvement with the students has been ‘really fantastic – a very good soil for growing big things in, even more so given the open, knowledgeable approach of the management, the musicians and the students.’

So what prompted this upping of the ante? Why all the fringe activities? ‘Partly it was Thomas [Søndergård] wanting to introduce us to his world and his influences, his desire to do more than just conduct pieces he likes’, says Garvey. ‘But more obviously, if you’ve got someone of Tommy’s talent, who the musicians clearly enjoy working with, who brings music to Wales that you can really get into, then why wouldn’t you use that person as much as possible?’

Particularly interesting was the decision from BBC NOW bosses to have Andersson visit as a conductor (until recently his primary occupation in Sweden) contextualising his own creativity with an entire concert of Romantic and 20th-century music from his homeland – all the more important in a year when Sweden can look like a musical poor Nordic relation while the world is busy trumpeting anniversary composers from Finland and Denmark.

‘I wanted to open the eyes of this very enthusiastic Welsh audience to the fact that there is much more Swedish music from that period than you probably think’ says Andersson. ‘So we played Hugo Alfvén’s biggest symphony, No 4, a fantastic ballet suite by Hilding Rosenberg and music by Ludvig Norman and Ingvar Lildholm. We don’t have a Sibelius or a Grieg or a Nielsen in Sweden, but we do have quite a few talents and I wanted people to hear them.’

Conducting the orchestra, and in expression-fuelled works that you might assume are in the composer’s DNA, proved a catalyst for Andersson. ‘That reinforced and changed and shaped the relationship a lot’ he says. It’s tempting to suggest that these Romantic and 20^th-century pieces, which the orchestra could easily discern and get their teeth into, were a good ‘way in’ for each party; groundwork for the more elusive business of Andersson instructing the orchestra in the performance of his own more complex scores. But in truth, Andersson’s music fits that ‘easily discernable’ description too.

The reason the BBC NOW’s announcement last year actually was something of a ‘Rattle goes to the LSO’ moment for me is that I’d coincidentally spent the few weeks before it listening to Andersson’s music on a CD issued back in 2009, and feeling energised by what I heard. The centrepiece of that recording is the last piece of Andersson’s that will be heard in Cardiff during his tenure at the orchestra – Satyricon, a ‘choreographic poem for large orchestra’ in which two yearning, romantically-inclined episodes are interrupted by grotesque, pile-driving modernist dances. I wouldn’t mind betting that the St David’s Hall audience will like it a lot.

It would be a safe bet, given the precedents. Audience reactions to Andersson’s works are telling. Not for him the slippery trickery of an orchestral canvas fashioned for the purposeful raising of eyebrows or throwing down of conceptual gauntlets. His music has a lucidity and clarity that’s characteristic of music from the Nordic region written in the last few decades. It also has an honest, directional style generally free of trend that tends to result in people enjoying it when it’s played for them. ‘I do think of an audience when I write’ the composer says. ‘Not in a cheap or flirtatious way, but in the sense that there’s a narrative aspect to my works however harsh they are. You need to win the musicians round in order to convey the meaning of the music to the audience. What’s the purpose of writing music that nobody wants to conduct, nobody wants to play and nobody wants to hear? I’m sure there are many contemporary music people who think my works are irrelevant or obsolete but to be honest, nowadays, and perhaps I’m getting older, I don’t really care about that.’

It isn’t about lightness versus gravitas, but rather communicative strength and the associated emotional residue – themselves results, perhaps, of Sweden’s lack of a single compositional figurehead that composers are unhelpfully pegged to. But it’s also relevant for Andersson’s BBC NOW position. If you’re going to have a composer spend a year with an orchestra that has a loyal following and no direct competitors in the same town, it’s important to know those followers will have some chance to build a positive relationship with the music. ‘It helps that there is a physical quality to the music’, says conductor Thomas Søndergård. ‘Tommy knows what works well with an orchestra but he also isn’t scared to do unusual things and he doesn’t get impatient – like in the really quite long, slow section of The Garden of Delights. As a listener you can fall into a state [in that passage] that other composers might not dare take you to.’ But it also helps that Andersson is spending so much time here. ‘There aren’t many composers who would visit us six times in one season’ says David Hopkins from the BBC NOW management team; ‘it means there’s a real chance for the Cardiff audience to get to know him. And the orchestra too.’

Which brings us back to that concert at Hoddinott Hall in February. It opened with a Percussion Concerto, Apollo, which absolutely didn’t do the fast-normalising percussion concerto ‘thing’ of having an athletic player run spectacularly about the stage knocking the stuffing out of everything – kitchen sink included. Instead, it was characterised by a sort of gentle, luminous pattering. Andersson’s wild, fantasy-strewn reimagining of Bach’s C minor Passacaglia showed how he could push a symphony orchestra to its absolute sonic limits, while his ballet score Warriors did the same to conventional tonality. Both drew some sharpened breaths from the Hoddinott Hall audience and in-play smiles from members of the BBC NOW.

The fact the musicians could so obviously get their teeth into these scores says something about their construction. ‘Tommy’s knowledge about how an orchestra works best is immense’ says Søndergård. ‘It has everything to do with his expression of what he wants in the detail of a piece: either by limiting the opportunities for a specific instrument or section, or doing exactly the opposite.’

In that rather bureaucratic description is distilled, you could say, the craft of the orchestrator and the composer. But it seems as though orchestras and their conductors are looking for rather more than the production of worthwhile music when tying a creative soul to their organisation for a length of time.

And that can only be a good thing. Søndergård, who has often called his old friend Andersson when building orchestral programmes because ‘he has great ideas about how to pair things in a concert’, knows it. ‘We must connect the audience, the composer, the conductor and the orchestra as much as we can’ says Søndergård. ‘We have someone here who is in dialogue with the musicians even when he’s not conducting, and I think that has been evident this week. Tommy is not just a composer, he’s many things and the more we can use him the better.’ The Nordic countries have long placed an importance on their own living composers, sometimes even granting them a government stipend in the belief that, if encouraged, they’re often extremely useful. If that proves another Nordic trend heading to these shores, we’ll all feel the benefits.

You can listen to B Tommy Andersson's music performed by the BBC NOW on the BBC iPlayer for a limited time: Warriors ('Afternoon on 3', April 20, 15.45); Passacaglia ('Afternoon on 3', April 24, 16.05)