Genius Within: The Inner Life of Glenn Gould, directed by Michèle Hozer and Peter Raymont

Today at the Liberty Theatre at 9.15 p.m. and tomorrow at 1 p.m.

Glenn Gould has been described as "arguably the most documented classical musician of the last century".

So it is with some shame that I admit here I knew absolutely nothing about him before watching this documentary.

Happily, I'm now pretty well-informed — and eager to hear some of the Canadian pianist's performances in more depth. Gould died in 1982 at the age of 50 after a glittering career in music.

He performed his (often controversial) interpretations of the work of famous composers around the world to adoring audiences until he stopped performing in public in 1964.

Gould was also known as a writer, composer, conductor and prolific broadcaster.

A huge amount of film footage and radio recordings of him exist and this film weaves much of it together wonderfully to tell the story of his life.

Like many an artistic genius, Gould was hugely eccentric — as so many of those interviewed in Michèle Hozer and Peter Raymont's film attest.

He had perfect pitch and could read music before he could read words but had an awkward relationship with his parents, was a hypochondriac and became obsessed with manipulating his public persona before his death. He once said: "I'm very much the anti-hero in real life but I compensate madly in my dreams."

This documentary manages to get behind that façade to trace both his personal and professional existence. The directors talked to a vast array of Gould's friends and colleagues for this movie, many of whom had never spoken publicly about him before.

The most illuminating descriptions of Gould come from the now adult children of painter Cornelia Foss, with whom the musician had a long-running affair.

Their lives were turned upside down and their loyalties were clearly torn when Foss left their father for Gould.

But they speak of him as a kind and loving man to live with, the epitome of the word avuncular, according to Foss's son.

I loved another quote from the son: "People lead eccentric lives sometimes and it doesn't have to make sense."

That pretty much seems to sums up Gould's existence. One friend talks about the fact that he was tortured — despite having little to be tortured about.

Whatever the cause of his inner turmoil, it resulted in some astonishing work, as his millions of fans around the world can testify.

• Genius Within: The Inner Life of Glenn Gould is showing today (Wednesday) at 9.15 p.m. and tomorrow (Thursday) at 1 p.m. at the Liberty Theatre.