The Grammy and Oscar-winner announced the 13-track album Harlequin on Tuesday, just days ahead of its Friday release.
"It's all these really interesting original productions," Lady Gaga told Reuters on the red carpet at the Joker: Folie à Deux London premiere on Wednesday.
"It has so much of the music that's in Joker as well as some original pieces that I wrote for the film and one that's for the album only, which is called Happy Mistake," she said.
The 38-year-old musician has simultaneously been working on her upcoming studio album, dubbed LG7.
"My studio album is coming out in February and my first single is coming out really soon, so I'm excited about that too," she said.
In her latest screen role, the A Star Is Born and House of Gucci actress plays Joker's love interest Harleen Quinzel, aka Harley Quinn.
Joker: Folie à Deux picks up where the original 2019 movie ended, with Arthur Fleck/Joker (Joaquin Phoenix) locked up in a high-security prison awaiting trial for multiple murder.
In jail he is captivated by Quinzel, an asylum patient, who reciprocates his passion. Their intense love story is played out in song-and-dance routines.
"The whole experience inspired me through and through," said Lady Gaga.
"It was so amazing to get to know this character through music, through this script, through dance, through all this tremendous collaboration," she said, adding it had been hard to let go of Harley Quinn at the end of filming.
"You know, I don't really know if I did because I made a whole record about her."
Joker: Folie à Deux begins its global cinematic rollout on October 1.
