"I think it's just moving on. It's rediscovering something else," said Phoenix, 34, said in an interview with Associated Press Television News before Saturday's American Film Institute festival, which also premiered "Che," starring Benicio Del Toro.
"Two Lovers" is his last film, he said. His publicist had disclosed Friday that the actor intended to focus on music.
Phoenix first mentioned his decision to "Extra" early last week at a fundraiser in San Francisco. He abruptly ended that interview after the reporter wondered whether he was joking about giving up acting for music.
Phoenix learned to play guitar and did his own singing to play country legend Johnny Cash in "Walk the Line," which earned him an Academy Award nomination. His publicist also said Phoenix has been directing music videos in recent years.
"It's like greener pastures, you know what I mean?" Phoenix said Saturday. "And so, I'm just going to try and like, I'll just be doing the other thing. ... Hopefully, I will emotionally impact you with that, as well."
"Two Lovers" stars Phoenix as a heartbroken man torn between a needy, neurotic neighbor (Gwyneth Paltrow) and the sensible woman (Vinessa Shaw) his parents want him to marry. The film, due in theaters early next year, was directed by James Gray, with whom Phoenix also worked on "We Own the Night" and "The Yards."