According to the 49-year-old Brazilian native, he cast Mars after watching him perform on Saturday Night Live. Saldanha even rewrote the character to be less "macho" so that it could fit with Mars' singing.
"He pushed it in a way that said 'this is the character' and we felt we could push it," Saldanha said.
As for Monae's role, Saldanha said he decided to cast her after meeting her at Rock in Rio two years ago.
"She had a few Brazilians in her band and I think that helped when I asked her if she wanted to sing in the sequel," he explained. "The music was much more integral to this movie and we started much earlier on the music."
Monae's "What Is Love" is the film's opening track. The soundtrack, which will be released around the time Rio 2 hits theaters on April 11, includes new songs from Mars, Philip Lawrence, and Kristen Chenoweth. Saldanha said the record will likely include 12 tracks and that all of them will be rooted in Brazil's traditional folk music. The director used a 12-member Sao Paulo band that only uses vocals and body percussion called Barbatuques to contribute to the score.