Sometimes a musical work of art is so perfect, so magnificent, that it’s almost impossible to remember the work that’s gone on, behind the scenes, from the early drafts to the anxiety and relief of the first performance. That’s certainly true of a masterpiece such as Bach’s St Matthew Passion. But writer James Runcie wants us to think about what went on in Bach’s mind while he was creating that magnificent Passion, and he’s written both a play and a novel about it. The novel, his twelfth, is called The Great Passion and it was published earlier this year; it was also broadcast on Radio 4 just before Easter.

James is an award-wining film-maker, playwright and artistic director who has worked at the BBC, the Bath Literary Festival and Southbank Centre. He’s also the author of the Grantchester detective novels, now filming their eighth series for television. The hero’s a young priest, who solves crimes while wrestling with problems of religious faith - and religion is something James Runcie knows all about, as his father was Archbishop of Canterbury.

In conversation with Michael Berkeley, James Runcie talks about the influence of his father, and of his unconventional mother, who was a pianist and piano teacher; in their household, he says, religion was optional, but music was compulsory. He shares his passion for the works of Bach in three of his choices, including the Matthew Passion. And he talks movingly about the death of his wife, the drama director Marilyn Imrie, from Motor Neurone Disease. When she was no longer able to speak, he played her music.

A Loftus Media production for BBC Radio 3 Produced by Elizabeth Burke