Joaquin Phoenix and Lady Gaga didn’t worry about occasionally singing off key. That’s because the stars of “Joker: Folie à Deux” were more concerned with delivering performances that felt honest and true when it came to performing their elaborate musical numbers.

"It was important to me that we never perform the songs the way you normally do them in a musical," Phoenix told Variety for a cover story on his "Joker: Folie à Deux" director Todd Phillips. "We didn't want vibrato and perfect notes." Instead, the pair "went with the emotion" and tried to be "true to the moment" above all else.

The film is a sequel to 2019's "Joker," which grossed $1 billion at the box office. In the sequel, Phoenix once again plays Arthur Fleck, an aspiring comedian who is committed to a psychiatric ward after murdering a talk show host (Robert De Niro) on live television while dressed as a clown. Arthur's shocking act of violence inspires a wave of followers, including a fellow patient, Harleen "Lee" Quinzell (Gaga), better known in the comics as Harley Quinn.

Lee and an army of disaffected Gotham residents believe that Arthur's alter ego, the Joker, is some kind of prophet. But things get really weird when Arthur and Lee end up in a psychotic duet. But the film isn't a traditional musical — Phoenix and Gaga's characters sing and dance, and many of their songs exist in their deranged minds. "Some of the music is fantasy, some of it is in the scene," Gaga explains. "It breaks the genre."