It was 40 years ago when Louis Fremaux, principal conductor of the City of Birmingham Symphony Orchestra , and Gordon Clinton, the much-respected baritone who was now principal of the Birmingham School of Music, put their heads together and came up with the idea of forming a CBSO Chorus.

Previously the CBSO had predominantly called upon the City of Birmingham Choir for partnership in major choral works, but now it was felt that there was a need for a chorus which would be under the CBSO’s full control, and which could be called upon for all those finales in which the chorus becomes an extra instrument.

As Beresford King-Smith tells us in Crescendo!, his history of the CBSO published to mark its 75th anniversary, admission standards were high: “The new choir was to be young and fresh-sounding, so an upper age limit of 45 was set.”

Pragmatically, that age limit has nowadays been abandoned, so the CBSO Chorus is now an invigorating mixture of youthful enthusiasm and well-honed experience.

So the CBSO Chorus is 40 years old. Thirty years ago the young Simon Halsey took on the mantle of chorus director, and he was immediately plunged in at the deep end, as he remembers.

“I began with the CBSO Chorus on January 1, 1983. We recorded Britten’s War Requiem some five weeks later. It was a baptism by fire. I was just 24 years old and in retrospect was very inexperienced.

“Whilst on a tour of the Highlands, I had answered an advert for the vacant post of Director of Music at the University of Warwick .

“I said, ‘You’ll never consider me, I’m far too inexperienced, but I still think I’d do a good job!’

“The university decided to interview me, put me on the final shortlist and invited the 25-year-old Simon Rattle (recently appointed at the CBSO) to choose between the three candidates. I got the job!

“About 18 months later, Beresford King-Smith invited me to do a CBSO Chorus rehearsal. One thing led to another and on November 5 1982, as I was sitting in my university office, Ed Smith (CBSO chief executive officer) called me and offered me the CBSO Chorus job.

“On November 5 – that date again – 1985, Simon Rattle took me aside and told me, with great candour, that I should concentrate on trying to become a good symphonic chorus master, that it was a fine calling in its own right and that I should not follow the orchestral conducting path – ‘the world has enough second rate orchestral conductors already!’

“And on that day, taking his advice, began the partnership that has defined my subsequent working life. I just love training choirs for the orchestral repertoire and over the last 30 years, by trial and error, I’ve learned the job.

“But my way won’t do in the future, and so I’ve founded a Master of Arts course in Choral Conducting at the University of Birmingham to train the symphonic chorus masters of future generations. It’s the only course of its sort in the world.

“I was recently lucky enough to train the BBC Proms Youth Choir (including singers from the CBSO Youth Chorus) for Sakari Oramo’s first Prom as chief conductor of the BBC Symphony Orchestra. And I’ve worked with him often in Berlin and Helsinki too.

“He’s wonderful – so laid back but in control, so good with each individual singer.

“Andris Nelsons – well, it’s a privilege! To see him draw the best out of the CBSO Chorus is a joy. He just gets better and better with them. All in all, I do not believe I could have worked anywhere and encountered such extraordinary colleagues. I’m blessed.”

The CBSO Chorus is much in demand elsewhere. How does Simon send them out into the world?

“Our first duty is to the CBSO,” he declares. “If there’s any time left over, or if other orchestras want the repertoire we are doing in Birmingham, then we’ll tour.

“We have a strong relationship with the BBC Philharmonic in Manchester. And we’ve been invited to sing throughout Europe with great orchestras that do not have their own chorus.”

The CBSO Chorus has also expanded into its various offshoots over the years.

“When I began, we had the CBSO Chorus with 130 members – in the Town Hall. We had to grow to 160-plus once we got into Symphony Hall.

“Then we founded the two Youth Choruses as part of the expansion into youth and community work, over 20 years ago. Practically every British orchestra (and those in Australia) have directly followed our example.

“Then came Young Voices (in association with the City’s Music Service) and recently our choral department joined up with our education department to found community choirs (such as Handsworth) and schools’ projects, which have inspired similar ones at the Berlin Philharmonic and at the LSO.”

Simon’s work has taken him all over Europe and beyond, often flying between engagements on an impossibly tight schedule. I once bumped into him on a flight from Amsterdam, having just finished a choral rehearsal there, and hurtling to a CBSO Chorus rehearsal a couple of hours later. But now he’s drawing in his horns a little, and returning to his home base in Shakespeare’s Forest of Arden.

“I’m thrilled to come home and see if doing less travelling I can really concentrate on the CBSO family, the university and to make sure that we continue to innovate and make a difference in the future.”