DANIEL Hart believes in suffering for his art. "I think you have to suffer slightly every time you play a character if you want to get to something special," says the actor, playing composer Wolfgang Amadeus Mozart on stage at York Theatre Royal.

"You have to decide at which point to sacrifice your own mind. For at least a month you're giving up certain pleasures during rehearsals. Mozart isn't easy to leave behind at the end of the day, but the cast has bonded and we go out at night."

He's not suffering as much as the piano in the rehearsal room. The legs were being sawn off when I arrived, lowering it to enable the audience to see Hart playing standing up in Peter Shaffer's award-winning Amadeus.

The play pits the giggling, childish Mozart against his arch-rival Salieri, whose nose is pushed out of joint by the young upstart's rising popularity.

The role combines Hart's two loves, acting and music. When he's not being an actor, he's writing and performing with his group JD3.

"I play the piano, but in a different style to Mozart," he says. "I learnt as a child for a while. Then I rebelled and got into rock music, and wanted to be like the Beatles and Michael Jackson. I've retained a lot of the technique because I love music as a whole."

Mozart was originally played on stage, at London's National Theatre, by Simon Callow and then on screen by American actor Tom Hulce. It's a great role for a young actor and Hart wants to "make it large but make it real", to give the character the authenticity it deserves.

"That period was incredibly flamboyant and bizarre, and people felt they could behave in outlandish ways," he explains.

"It's all a bit like when rock and roll came along. Some musicians were wearing cardigans and some were wearing tight leather jeans. It's like the youth culture of 1956 and 1967 all at once.

"As Amadeus, I represent the rock and roll lifestyle. You could play him as this hysterical puppet, but that's not what he is. He's just incredibly driven.

"Until the Mozart generation came along, music was very classical in that it was just one theme being repeated. Things changed so rapidly in the way of thinking about music. The idea of a hook in pop music was thought of at that time."

Hart has never seen Amadeus on stage, and hasn't seen the Milos Forman screen version since he was about nine. But he remembers the music affecting him, along with the darkness of the latter stages of the film.

In preparation, he watched a French movie about Beaumarchais to pick up the gestures and attitudes of court behaviour of the period. He's been careful not to do too much research, as the play is a fantasy and too much information could conflict with what goes on in it. What were helpful were Mozart's letters, as the way he expresses himself in them is similar to his behaviour in Shaffer's play.

Director Tim Luscombe offered Hart the role after seeing him in a production in London. His theatre roles since leaving the Drama Centre, with the BBC Radio Carleton Hobbs Award, have included parts in The Winslow Boy, Madame Melville and as Michael Darling in Peter Pan at the National.

On TV, he was in the BBC's Vanity Fair and the recent Cambridge Spies, in which he shared a love scene with Tom Hollander - "in front of lots of sweaty technicians, so that was a challenge."

After doing mainly modern drama, he's pleased with the chance to dress up in fancy clothes and wigs. "At drama school, you get to wear lots of flamboyant, ridiculous costumes. But, in the business, a production like Amadeus only usually occurs in large theatres," he says.

For someone "used to being in a room with two people", being part of a cast of 23 is something of a shock, although a pleasant one.

The music is a bonus too. Music, he feels, "allows you to be yourself completely, feel what you're feeling and, like writing a diary, helps you realise where you are at".

JD3 comprises Hart and a friend. He describes their output as avant garde with classical elements. He's keen to keep the two aspects of his life separate. "Acting and performing as a musician are two very different things. I have to be careful and selective how I arrange my calendar," he says.

* Amadeus: York Theatre Royal, July 18 to August 9. Tickets (01904) 623568.