Bradley Cooper's lengthy Maestro transformation

Bradley Cooper wore 137 individual prosthetics in 'Maestro'.

The 48-year-old actor portrays late legendary conductor Leonard Bernstein in the movie and he worked closely with make-up effects expert Kazu Hiro - who won an Oscar for his work with Gary Oldman in 'Darkest Hour' - for his dramatic transformation, spending five hours in the make-up chair to alter his appearance each day.

Kazu devised four full sets of prosthetics and two bodysuits to document the New York Philharmonic music director - who died in 1990 aged 72 -over the passing over time from the early days of his career in 1943 up until the last years of his life.

He told People magazine: "All in all, I crafted 137 individual pieces, ranging from small to large."

And it wasn't just Bernstein's physical appearance Bradley was trying to transform, as the effects expert constructed a special nose plug for the actor which, as well as changing the shape of his hooter, altered his intonations so his voice could more closely mimic the nasal tones of the music legend.

Kazy said: "Bradley's transparency and relentless pursuit of perfection were awe-inspiring."

Costume designer Mark Bridges studied photos of Bernstein to recreate his outfits.

He said: "He looked so smashing, and if it works, don't fix it."

The transformation left the composer's three children, Jamie, 71, Alexander, 68, and 61-year-old Nina, stunned.

Jamie said: "We had no idea that Bradley had this level of intensity and commitment about a thing when he got it in his grip. There are even certain moments in the film, when he's in motion, where he looks so exactly like our dad it makes us gasp."

The 'Silver Linings Playbook' star was in constant contact with the Bernstein family as he worked on the movie, which he also directed.

Jamie said: "The way he embraced us as he went along in this project — he was so open-hearted. We wound up feeling like we could trust him."