"I worked on it. It was fun. Of course, I loved doing it," Keaton told UPI during a round-table interview with reporters in New York Tuesday.
"I had insane fantasies about me and my singing, but they completely fell apart when I started singing. You know what I mean? It's sort of like a little, tiny voice and not much there. I wish it had been a big voice. I mean, can you imagine singing great? Can you imagine having a gift like Beyonce's singing? That coming out of your head? What does it feel like? I would love it. So, when I was trying to do the Bonnie Raitt song, I was really having a hard time. I couldn't really do the notes. I couldn't be Bonnie Raitt."
So, what was it like singing in front of music icon Frankie Valli, who has a cameo as a nightclub owner in the movie?
"That was scary," the 68-year-old actress confessed.
"He was, like, playing his part. I think he was thinking about himself. I don't think he was thinking: 'Oh, that Diane! Oh, wow!' He was way back in a corner. He was very nice when I met him. People usually are."