IN the 46 years since it was formed by Arthur Oldham in 1965, the Edinburgh Festival Chorus has delivered some of the biggest and most memorable walls of sound, with some of the world's top professional orchestras and celebrated conductors.

From Mahler’s Symphony No 8 under Alexander Gibson, Verdi’s Requiem under Carlo Maria Giulini, Bach’s Magnificat under Herbert von Karajan, Mahler’s Resurrection under Leonard Bernstein and, more recently, Tippett’s A Child of Our Times, it has carved its niche in the annual international cultural fest.

The range of music learned and sight-sung every year by the 77 women and 47 men who make up the core chorus is vast, and this year’s festival is no less challenging.

Tonight’s opening concert performance of Schumann’s Das Paradies und die Peri with the Scottish Chamber Orchestra led by Roger Norrington is followed on Thursday by Massenet’s Thaïs, with the Royal Scottish National Orchestra under Andrew Davis; works by Weber, Mendelssohn and Liszt with the Orchestra of the Age of Enlightenment, under the baton of Vladimir Jurowski, on August 26; Mahler’s stonking Symphony No 2 with the BBC Scottish Symphony Orchestra and Donald Runnicles on August 28; and Messaien, Bartok and Ravel with the Bamberg Symphony Orchestra conducted by Jonathan Nott on September 1 and 2.

The music programme is chosen each year by the festival director in accordance with his chosen theme, which means there’s a constant flux in the music to be learned.

This is what makes being a chorus member endlessly interesting – even for those who, like tenor David Arulanantham, have been in since the beginning. This year’s emphasis on new and early music, in a variety different languages and embracing a whole range of Western and Eastern cultural references, is exceptionally inspiring to the retired BP engineer and part-time lecturer at Aberdeen University, who joined the EFC in 1972 as a member of the now-defunct Aberdeen section.

“Even after 40 years I still feel the hairs on the back of my neck rising when we get together with the full orchestra,” he says. “That’s the moment you really feel you’re part of this huge, huge sound. I keep telling my friends that for a month every August I feel like I’m in musical heaven.”

His undimmed enthusiasm belies the hard work and absolute commitment demanded of chorus members, who are re-auditioned every year and are required to attend rehearsals every Tuesday evening in Edinburgh from October to June, and almost daily throughout August – no matter what their day job is, and regardless of where they live.

“When the chorus was formed in 1965 at the behest of Sir Alexander Gibson and Lord Harewood, he wanted it to be truly Scottish and founded major sections in Edinburgh, Glasgow and Aberdeen,” explains Arulanantham, who was born in Sri Lanka and studied in the then North Borneo (now Eastern Malaysia) before doing his degree at Aberdeen University. “There were between 30 and 30 members in Aberdeen and around 40 in Glasgow. Each section would rehearse separately in three different venues, only coming together in August for the festival.

“That meant we didn’t have the weekly commute to Edinburgh during the off season, and this arrangement continued until the 1980s when the Glasgow section was merged with Edinburgh under the reign of Frank Dunlop, and the Aberdeen section was axed.

“Then, when Brian McMaster took over as festival director, I was asked by the Aberdeen section members to talk to him and Oldham and persuade them to reinstate Aberdeen, which they did for a brief period. Unfortunately the financial situation meant Aberdeen was axed again and two or three of us stalwarts decided that if we wanted to join the top, we’d have to commute to Edinburgh.

“It’s well worth it, because as amateur singers it’s the only opportunity of singing at a professional level with professional orchestras. In Glasgow and Edinburgh choral singers also had the RSNO and SCO chorus, but in Aberdeen the EFC was all we had, and it was very precious to us.” He now divides his time between his home in Aberdeen and his house at Carlops outside Edinburgh.

Over the years since he joined, the chorus has shrunk from about 230 members to nearer 130.

Arulanantham says: “It was formed for large works like Mahler’s Symphony No 8 and we used to make a huge sound with 230 people. Then we started doing Bach and Mozart; more and more conductors don’t want that big noise, and choral singing has become less popular with the general public – though chorus master Christopher Bell has done wonders to redress that by bringing in younger voices from the National Youth Choir of Scotland and rejuvenating the sound.”

He added: “Over the past few years we’ve not done the big standard choral repertoire of Brahms and Verdi Requiems, but I’m not complaining because I’ve learned so much – notably James MacMillan’s St John Passion, Messiaen’s St Francis of Assisi, Bernstein’s Candide and Kurt Weill’s Rise and Fall of the City of Mahagonny. We’d never have done this if we’d stuck with the repertoire of standard choral societies. In this respect the EFC is unique in Scotland.”

While Arulanantham is looking forward to the opening concert of Schumann’s music, his colleague Valery Bryan is more stirred by Mahler’s Second Symphony and Ravel’s Daphnis et Chloe. Bryan is one of the newest recruits, and this festival will be her first since rejoining after a break of 26 years. She lives in Ullapool, has just retired as a music teacher, and makes the weekly commute to Edinburgh by Citylink coach.

“I can travel quite cheaply because I have my new senior citizens’ bus pass,” she laughs. “And I can learn the music, including the full orchestral score, on my iPod while travelling. It’s best to be familiar with the entire score because that way you know the cues.

“It’s an incredible commitment, but it’s worth it because it’s so rewarding. With the Edinburgh Festival Chorus we’re working at the top professional level even though we’re amateur. It’s good to feel like a small cog in a big wheel; I love being completely involved in something without the tension of being a soloist.

“I never thought this would happen and I’m very grateful to Christopher [Bell] for letting me back in after I left in 1975. It’s very precious to me.”

Changes during her period of absence include her own voice morphing from soprano to alto, and the injection of younger voices.

“There are lots of members apart from me who don’t live in Edinburgh and travel from places such as Falkirk, Glasgow and Stirling. They are working hard in their day jobs and the fact they are committed to attending rehearsals creates an energy and focus. They are there because they want to be, and will make l sacrifices to make sure they attend.

“There’s a real sense of everyone contributing to the greater whole. I feel that even more now, and am aware of how special it is. I don’t know how long I’ll be allowed to stay but I will enjoy it for as long as I can.”

Now in his late 60s, Arulanantham is daring to contemplate the previously unthinkable. “Being in the chorus is a huge commitment and very hard work. There are blocks of time when you can’t go on holiday, but now I’m retired I want to do other things and travel,” he says. “It’s very pleasing to know that there are so many young, well trained people in the chorus now. If I were to leave, I would feel less guilty because I know it is in very good hands.”

Edinburgh Festival Chorus joins the Scottish Chamber Orchestra at the Usher Hall for the 2011 Edinburgh International Festival opening concert tonight at the Usher Hall.