Justin Timberlake was nervous scoring Jessica Biel's The Book of Love

Mary Steenburgen was "honoured" to take part in the film alongside her longtime friends, Justin and Jessica.

Justin Timberlake was nervous to score his wife Jessica Biel's new drama The Book of Love, because it was his first time in charge of a film's music.

The Total Recall actress stars in and produces the movie, but it took her nine years to get the project to the big screen.

Due to her limited resources, she turned to her husband Justin to score the film, and her movie mother, Mary Steenburgen, reveals the pop superstar was actually anxious about the gig.

"Jessica produced it, and she called me years ago about playing this part," Mary recalled on U.S. breakfast show Today. "She and Justin Timberlake are dear friends of mine, and actually it was Justin's first score, so it was amazing to go through the process (with them).

"Believe it or not, he was actually nervous about it, which is hard to believe, but he did an amazing job and I was honoured to be in it with them and hang out in New Orleans with those guys."

In the film, Jason Sudeikis stars as a New Orleans, Louisiana architect who becomes friends with a homeless teen, played by Game of Thrones star Maisie Williams, following the death of his pregnant wife, portrayed by Biel.

Jessica previously admitted she forcibly recruited Justin to score The Book of Love after co-writer and director Bill Purple proposed the idea.

"Basically, it was, 'You're going to do this or there's going to be a problem - and you're not going to get paid. Love you, mean it'," she laughed at the New Orleans Film Festival in October (16).

She added, "Honestly, I think it's something he was really excited to do. He loved the script. He's been living with this script for a long time."

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