ANSWER:

If you believe in such lyrics, you are a kafir.

If you sing it without believing in it, this is sinful but not kufr as kufr requires belief. 

In a recent Q&A you said that thinking/playing kufr songs in mind is not kufr. But I am curious to know that if someone owing to thinking about such songs mistakenly ends up singing the lyrics will that be kufr?Many such songs are not wholly about kufr only a line or two are kufr and other lyrics are okay… So if someone ends up singing those parts of normal lyrics?

Sports, Entertainment and Music | October 10, 2021 8:41 am
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If a person plays/sings songs in his mind which has words of Shirk and Kufr but he does not say it with mouth only that song plays in his mind will this be considered as minor or major shirk or kufr or will he be sinful? Please specify.
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Is it permissible for a grown up woman to keep stuffed toys like a teddy bear, if not then toys which have only two eyes like a dot and a smile and no other features like ears or nose