You might think that running a 1,700-pupil comprehensive would be enough to keep a chap busy.

But Aydin Onac (pronounced Eye-din Ernatch), head of Tewkesbury school in Gloucestershire, has another string to his bow - or, more precisely, a whole keyboard.

On Sunday, at the Adrian Boult Hall in Birmingham, he will play Beethoven’s Emperor Concerto with the Birmingham Symphony Orchestra. Other engagements over the next year include Ravel’s G major concerto and Rachmaninov’s Third, perhaps the most testing of all. It makes, he says, for “an interesting lifestyle”. But he cannot imagine life without any of his passions: music, maths and education.

When on earth does he find time to practise? Between 6am and 8am, long before staff and pupils arrive, he is to be found at the grand piano in the school hall. It saves disturbing the peace at home and provides entertainment for the cleaners.

At 8am, he switches to headteacher mode and also fits in a fair bit of maths teaching during the day. At 6pm, he goes home and tries not to take his work with him.

But it would be wrong to say he rests. “Rest doesn’t really feature in my life,” says this serial high-achiever.

Mr Onac is the son of a Turk from a village on the slopes of Mount Ararat, who won a scholarship to study at Sheffield University and married an English teacher from Derbyshire. Mr Onac was born in the Peak District, attended grammar school (head boy, of course) and then went to London and studied at the Royal College of Music.

But, despite winning many prizes and making a sell-out debut at London’s Purcell Room, he struggled to earn more than pound;300 a year as a young soloist. So at 28 he took a maths degree at University College London, gained a first and, at 31, started a job in the City. But he hated it.

After three months of auditing, he told his boss he was going to leave.

Then, with no income and a wife and two young children to support, he stumbled upon his second vocation. At a party, he met David Grant, then head of Hemel Hempstead comprehensive and a former organ scholar, an encounter which led to an offer of a job as a maths teacher. The untrained Mr Onac jumped in at the deep end and swam.

After two years at Hemel Hempstead, he moved as head of maths to Bridgnorth in Shropshire and from there to a post as deputy head at the Chase, Malvern. He moved to Tewkesbury, a technology college and beacon school, last autumn.

Still only 51, he has fitted in much else: the creation of a top quality brass band which performs regularly at the Upton Jazz Festival, directing seven musicals, including one he wrote himself, and squash and mountain-climbing to fill idle moments.

“I’ve got a lot of energy,” is his barely adequate explanation. “And I get a huge buzz both out of running a large school, where there’s always something interesting happening, and out of music as well.”