COMPOSER Ailie Robertson dates her passion for music – and especially for her own instrument, the harp – to Christmas concerts when she sang in the choir of her school, George Watsons in Edinburgh. They included the participation of the Clarsach Society and she was immediately taken by the traditional version of the concert instrument and instigated a campaign of parental pressure to secure one.

She was learning to play piano, but took to the harp much more quickly, and performing as a harpist is still a huge part of her international musical life. At home, however, Scotland is beginning to know her much more for her writing – and the high-profile way she pursues the goal of making sure that new music is available to a wider public.

That evangelical zeal is likely to be even more evident with her appointment as composer-in-residence at the annual Sound festival in Aberdeen and its surrounding area, succeeding John De Simone. This is his final year in the job and Robertson’s appointment will run from 2019 to 2021, but there is an overlap with both composers having work in this year’s programme, which begins on Wednesday.

Sound director Fiona Robertson has instigated a thread of the festival that highlights “endangered instruments” – ones that are being learned by fewer young students – and this year that instrument is the viola, the larger cousin of the violin and the butt of orchestral jokes (often told by viola players). Sound will feature a great deal of music for viola, including a version of Thomas Tallis’s 40-part motet Spem in Alium arranged for 40 electric violas, and has composer Sally Beamish picking up her own instrument again to play in a viola sextet, including a new work she has written for the event herself.

Ailie Robertson’s own composition will sit alongside a piece for five violas by John Cage entitled Dream, but her remit was to come up with something that would work for any number of viola players, and which gave those of any standard of proficiency on the instrument something to do.

“It is about what music can be,” she says of the piece, which will be the culmination of a Viola Day led by virtuoso Garth Knox, and open to anyone to come and join in, even absolute beginners.

“We are not sure how many people will be there – it could be ten or a hundred, so the piece has to be very flexible and cater for any possible permutation.”

Robertson leaps to the defence of the much-maligned viola – “it is overlooked, but it has so much sonority and is so expressive” – but you suspect that the challenge of writing to such an open remit was as much of an attraction. Having responded to the open call for applicants to do the composer-in-residence job, she is waiting to learn how she can now respond to the different themes that arise at Sound during her tenure rather than having a list of works she would like to create for the event.

“The work for this year is an additional thing,” she says, “then we’ll see what suits the festival and works best for my own musical development.”

This year has already seen her music performed by the London Philharmonic Orchestra, at the St Magnus Festival in Orkney, by the Bang On A Can collective of New York City and at Celtic Connections in Glasgow, where her work The Seven Sorrows was one of this year’s New Voices commissions.

Her pedigree is arguably perfect for Celtic Connections, with credentials in both folk music and contemporary classical, although her first degree was as a scientist.

“I didn’t have the confidence to apply for music,” she says, “so I studied genetics at Cambridge. And although I loved the course, I hated working in a laboratory.”

Hence the unlikely leap to post-graduate studies in Limerick in Ireland, and a masters in traditional music performance, and thence a doctorate in composition at Trinity Laban in London.

“A lot of people take different routes to composition,” she says, “and I am so glad I didn’t do it when I was 17 years old. I am much more confident about my ideas, and I like being both a composer and performer now.”

That means that although she is happy to work on her own to fulfil commissions from a distance, the chance to create music in collaboration with other musicians is her preference.

“I want to keep both sides of my own musical life going, so I like to work with the performers as much as possible. It is not so satisfying just to send it off.”

The Seven Sorrows ticked that box in being written for string quartet, an alto singer and herself on harp and electronics. Premiered on the very last day of Celtic Connections at the start of February, it was inspired by the Gaelic grief ritual of keening, and an example of Robertson at her most experimental.

“I pushed the boat as far as I could, and that was quite far out, but I was delighted with the result.”

So far that has been the work’s only performance, but the composer is hopeful that it will have a further life, possibly with a tour. She maintains that the biggest obstacle to interesting people in new music is the off-putting way it is presented.

“I find that people are really quite open-minded and are usually interested in hearing something different, and are happy to sift through things that they might not like to find the thing they do.”

She compares the process to visiting an art gallery; even if you don’t like every picture you’ll find something that you do like – and she is active herself in making sure the music is presented in interesting new ways. In the spring of next year she will begin a series of events in club venue The Caves in Edinburgh putting the spotlight on new talent, with guitarist Sean Shibe the opening attraction.

Two years ago she was the driving force behind Echoes and Traces, a choral project in partnership with Historic Scotland that commissioned eight composers (including Beamish and herself) to write a work responding to the earliest piece of written harmony found in Scotland, a 12th century hymn to St Magnus, Nobilis Humilis. The pieces were performed by the choristers of Capella Nova in churches and other buildings across Scotland, drawing capacity houses for previously unheard work.

“If you want something to happen, you have to make it happen,” says Robertson. “There is no point just sitting at home waiting for a commission from the Scottish Chamber Orchestra.

“It is all about audience building, and it is the responsibility of us as composers to create opportunities. It is vital that everyone is doing as much as they can.”

There were many different reasons why people were interested enough to come to the Echoes and Traces concerts, she says, but the main thing was that they were each a one-off unmissable event.

“The challenge is to get people to leave their homes and come out and listen to a live concert – because there really is nothing like it!”

Sound festival runs from October 24 to November 4. www.sound-scotland.co.uk