What was your emotional response to seeing your parents – and yourself – depicted on screen?

The word that keeps coming up for my brother and sister and me is surreal. You can imagine how surreal it is to be watching an actor who is younger than yourself playing your father at five different ages. It’s all so phantasmagorical and disorientating – but in a really cool way!

This film that Bradley Cooper made is so unique, so idiosyncratic, so personal. And so not what this project began as 15 years ago, before Bradley was associated with it – the original notion was it would be a more standard biopic. Then when Bradley joined the project five years ago, he completely reinvented the approach and made it more into the portrait of a marriage. It’s like no other film about an illustrious person that you ever saw – it’s like he invented something brand new.

Describe your involvement in the film?

Once we agreed to let Bradley make this film, and he had this licence, he was free to do anything he wanted, and was not obligated to consult with us ever again if he didn’t want to. But he chose to keep us involved all the way along, and was so keen to achieve a kind of authenticity about the way he told the story that he consulted with my brother and sister and me about all sorts of things, sending us pictures, sending clips – and eventually he even filmed in our own house in Connecticut. But the one thing that we were not privy to was any of the actual filming.

What do you feel your father’s legacy is today – and what would you like him to be remembered for?

A few years ago it came to our attention that today’s music students don’t really know that much about Leonard Bernstein any more. Maybe they’ve seen West Side Story, maybe they’ve played the Candide Overture, but they don’t really know very much about him as a person and a musician, and why he still matters. And I was so taken aback to discover this that I created an hour-long presentation to take around to music students all over the US. And the name of this presentation gives it away: Leonard Bernstein, Citizen Artist.

The thing about my Dad is not only was he a composer and conductor and educator par excellence, but also – equally important – he was an activist and humanitarian, and went to every length he could think of to use his music-making to make the world a better place.

Maestro is showing in selected cinemas, and on Netflix from December 20