Cher has never witnessed a fan master an impression of her legendary voice.

The Hollywood icon made an appearance on The Tonight Show Starring Jimmy Fallon on Monday night (15Apr19) to promote her new Broadway musical The Cher Show.

During the chat, host Jimmy did a spontaneous rendition of Cher's version of ABBA song Fernando, and the star was less than thrilled with his take.

"(Your impression) was terrible," she laughed. "But I don't mind it because I have never heard anybody who has ever done a good one. They just make some noises and facial expressions and I just try to find myself in there but it's just so much bulls**t."

Cher went on to explain that she isn't much of a fan of karaoke either, as she doesn't like to sing in front of "strange people" unless it is in a concert setting.

And interestingly, the Believe hitmaker used to find it difficult to perform in front of her husband and Sonny & Cher collaborator Sonny Bono.

"When Sonny was trying to teach me I Got You Babe, (one time he woke me up in the middle of the night), and said, 'Cher, come here.' 'Cause we only had furniture for one room. 'Cher, come here. I've got this song.' And so, he said, 'OK, I want you to sing so-and-so and so-and-so.' And I went, 'No, I don't,'" the 72-year-old recalled. "He said, 'Cher, it's me. Damn it. Just do it.' And then I did it. And I said, 'I don't think it's a good song. I'm going to bed.'"

Elsewhere in the interview, Cher confessed that she was "terribly" shy growing up, and emphasised that she finds it difficult to watch aspects of her life be depicted in The Cher Show, in which three actresses portray her at different stages.

"It was hard. There are things I put in it that I hesitated about but then I thought, 'If you're going to do something and people think they know you and you know they don't, then you gotta put in those unattractive parts,'" she insisted. "There are a couple parts where I just sob every time and I know it's coming."