Jennifer Garner wept with nerves as she recorded duet with Andrea Bocelli

Jennifer Garner had to keep her eyes covered while recording her duet with Andrea Bocelli because she kept crying due to nerves.

The 13 Going on 30 actress signed on to sing Dormi Dormi Lullaby with the Italian tenor for his Si Forever: The Diamond Edition album, which was released in November.

Recalling the experience during an interview with chat show host Ellen DeGeneres, Garner admitted she got singing lessons to prepare for the duet and was so nervous on the day that she couldn't stop crying.

'Is that the craziest thing?" she marvelled. "If you just said list the 10 craziest things that have happened in your life, that would be on there. I think they had recorded this beautiful lullaby and they wanted a more of a mom person, who was less of a singer singer, so they came to me.

"But then it turns out I had to really sing, so I had months of lessons. I was so incredibly nervous: I cried in the parking lot, I cried while I was recording it.

"I had to keep my eyes covered to deal with the fact that I was even recording it! Mr. Bocelli wasn't there, but he was in my ears... and so I could hear his voice and it just is so magnificent it just kind of lifted me up and I did it."

Despite her nerves, the 48-year-old, who shares three children with her ex-husband Ben Affleck, was thrilled with the recording process.

"I have always had an affinity with classical music and I'm a sucker for a love song. It was fun and enlightening to sing in Italian - a real joy to record," she added.