Video: Joaquin Phoenix and Lady Gaga Talk Singing Live for JOKER: FOLIE A DEUX

Joker stars Joaquin Phoenix and Lady Gaga, along with director Todd Philips, sat down with Good Morning America for a segment about the highly-anticipated sequel to the 2019 film. 

As previously reported, the new movie heavily features musical sequences reminiscent of classic MGM musicals. Get Happy,” “For Once in My Life” and “That’s Life" are among the songs confirmed to be featured in the movie, which the actors sang live on set.

"When we first started, I did not want anything to be spontaneous. I wanted to sound as good as possible," Phoenix explained. It was Gaga's suggestion to do the numbers live and, despite his initial reservations, he credits the superstar for ultimately helping him feel comfortable on set.

"I can assure you that Joaquin, using his natural voice, was so much more compelling than any lip-syncing would ever be," Gaga said.

As for her performance, she adjusted her vocals to fit the needs of the character she is playing, Lee Quinzel- also known as Harley Quinn.

"Lee is not a performer and I am. In a scene, as a different character, it's just completely different. It's Lee's reality [and] their shared reality," she told GMA.

The musician has also just released a companion album to her character, fittingly titled Harlequin. The album, which incorporated music from the film, is available now.

Joker: Folie À Deux finds Arthur Fleck (Joaquin Phoenix) institutionalized at Arkham awaiting trial for his crimes as Joker. While struggling with his dual identity, Arthur not only stumbles upon true love, but also finds the music that's always been inside him. 

In addition to Lady Gaga and Joaquin Phoenix, the cast of the film features Emmy nominee Zazie Beetz, and Oscar nominees Catherine Keener and Brendan Gleeson. Joker: Folie À Deux will be released in theaters on October 4.