Yeah, when hamis is used to describe people, good translations are usually along the lines of fake, phony, insincere, not genuine, a fraud...
I guess this sentence would only be said while listening to a singer singing off-key. It could be "the orchestra is perfect but the singer is out of tune". Right?
Oh, yes, with a musician it could be talking about being off pitch / out of tune!
Talk about singers. :)
There is another word, "fals", that is obviously related to "false". It may not be frequently used, or just went out of fashion. But it is more specific to being out of tune.
The word "hamis" can also be used to describe something that is a fake. Like a counterfeit bill, etc.
So, if I understand correctly, we could either be describing her singing as being off tune or describing her personality as insincere?