AceShowbiz - Christina Aguilera has included her daughter's voice on her latest album.

The superstar released her eighth studio album "Liberation" on Friday, June 15, with the record featuring collaborations with artists such as Demi Lovato, Ty Dolla $ign and 2 Chainz.

But during an interview on "The Tonight Show Starring Jimmy Fallon" on Thursday night, Christina shared that her three-year-old daughter Summer Rain, who she shares with fiance Matthew Rutler, can be heard on the album too.

"Her voice is on the album," she said, without divulging which track Summer's voice can be heard on.

However, Christina admitted that Summer wasn't too bothered about being on the record, and in fact, gets annoyed by her mother's singing.

"When I'm doing my vocal warm-ups, she slams the door and is like, 'You are interrupting (children's cartoon) Peppa Pig.' It's hilarious," the 37-year-old laughed, adding that her little girl is also obsessed with the music in kids' TV shows like Paw Patrol and PJ Masks. "She wants a PJ Masks birthday party. She makes me sing it to her every night, so I do a lullaby version for her. But it's a hard song to slow down and she won't let me skip a lyric either!"

Prior to Christina's interview, host Jimmy Fallon aired a clip showing how he and the blonde star went incognito and surprised an unsuspecting crowd at a New York subway station with a performance.

Disguised in costumes and wigs, Christina and Jimmy belted out Aretha Franklin's "Think", drawing in a huge crowd of commuters who all began filming the show on their phones.

The duo then removed their outfits to display their true identities and went on to sing Christina's song "Fighter", from her 2002 album "Stripped".