How Carey Mulligan Celebrated Her Oscar Nomination: 'Everyone Screamed, My Baby Started Crying' (Exclusive)

Carey Mulligan's youngest child got quite the scare when it was announced that Mom had been nominated for an Oscar.

"When my name came up, everyone screamed, and my baby started crying," Mulligan, who shares three kids with husband Marcus Mumford, tells PEOPLE.

In Maestro, the London-born star, 38, plays actress Felicia Montealegre, the wife of legendary composer Leonard Bernstein, portrayed by Bradley Cooper, who is also nominated.

Mulligan has said she was intrigued by the real-life couple's complicated relationship.

"I think they had an incredible life. They've got, you know, three wonderful children, and they've left behind this incredible legacy of love. But I think there is a universality to the film in that it is a depiction of a marriage, you know, and every marriage, regardless of any of the details, is deeply complicated and very challenging at times," she told NPR.

For PEOPLE's annual Oscar portfolio in this week's issue, Mulligan and Cooper, 49, sat down to discuss the film, their friendship and their love of music.

"Music's always been a big part of my life in lots of ways before I started acting at all," says Mulligan. "My grandmother, I used to sing with her. She's Welsh. She passed away, sadly. But singing is a huge part of Welsh culture."

Mulligan, who has been married to the Mumford & Sons lead singer since 2012, adds, "I grew up singing and loving music and then married a musician."

The 96th Academy Awards, hosted by Jimmy Kimmel, will air live on Sunday, March 10, from the Dolby Theatre in Hollywood, California, beginning at 7 p.m. ET.