Joseph Haydn was, without question, one of the towering figures of the classical period. Somewhat hidden in his considerable shadow is his younger brother, Michael.
It's ironic now to note that their parents had higher hopes for their younger son, already a Vienna Cathedral organist at the age of 12.
The path he took brought him close to another of music's major families - the Mozarts.
Michael would become a colleague of Leopold Mozart, and, though much older, a friend of Leopold's son, Wolfgang Amadeus.
To follow the story, we must head for Salzburg in Austria, where Wolfgang was born in 1756. Thirteen years earlier, his father had joined the court orchestra there.
Back in Vienna, Michael Haydn was singing in the cathedral choir alongside his elder brother.
When his voice broke, and he lost his place in the choir, he stayed in the city, developing as a composer, and supporting himself as a freelance musician.
He got his first regular job in a court orchestra in what is now part of Romania. A talented violinist as well as an organist, he was in demand.
After two years there, he was spotted by the nephew of the Prince-Archbishop of Salzburg who recommended him to his uncle.
The paths of Michael Haydn and Leopold Mozart crossed when Michael was appointed Konzertmeister, or leader of the orchestra, at the Salzburg court.
Within months, Leopold had been promoted to the position of deputy to the Kapellmeister, or head of music, but by now he was making other plans. His six-year-old son has turned out to be a child prodigy. He was determined he would get the success he deserved.
So while Michael Haydn devoted himself to his duties at home, expanding his repertoire, Leopold was taking his family on tour.
Haydn became very well-regarded. When the Prince-Archbishop died in 1771, it was Michael Haydn who composed his Requiem Mass, a considerable feat in the space of only a fortnight.
His position was secure enough that he was kept on by his successor as Prince-Archbishop, Hieronymus von Colloredo. Though the new man's tastes were very different to the baroque grandeur that his predecessor had favoured, Haydn was able to adapt, developing music in a more austere style.
In 1777, the top job - Kapellmeister - became vacant. Michael Haydn was a candidate, but Leopold felt it would be perfect for his son.
In a rather ham-fisted attempt to canvass for Wolfgang, the elder Mozart wrote a notorious letter to the archbishop suggesting that Haydn was unsuitable for the post. He was too fond of a drink and he was lazy, Leopold alleged.
It made no difference. Haydn didn't get the job, but nor did Wolfgang Amadeus. The boss preferred not to promote from within.
It would hardly have worked out for the younger Mozart. He felt he wasn't appreciated. He wanted to expand his career. He had developed a sense of his own worth.
Things came to a head when he handed in his resignation. The archbishop refused to accept it.
A stand-off ensued which ended, as he would relate to his father, with Mozart being shown the door, sent on his way by the butler "with a kick in the ass".
Michael Haydn took over his position as court organist in Salzburg, and the pair remained friends. And, strange as it may seem, they share a symphony.
Michael Haydn's 25th got its first outing when Mozart presented it with an introduction that he had written. It came to be known as Mozart's 37th.
It would be over a hundred years before its true identity was discovered. When it was no longer one of Mozart's, it slipped quietly from the repertoire.