I know that intentionally playing blasphemous lyrics is kufr. What if a person is watching a video/movie and someone says something blasphemous in the video? Does the person watching the video blaspheme? Or is he still a Muslim? Because he didn’t know for sure that there would be blasphemy in the video and he didn’t intend to blaspheme.
A`udhu billahi min ash-shaytan ir-rajeem
Bismillahi ‘r-Rahmani ‘r-Raheem
If he watches only, it may be sinful.
If he repeats or follows or believes in what is said in a song e.g. “There is no religion that can save me…” or “I’ve been locked out of heaven…” that is Kufr.
The best is to learn Tawhid and ‘Aqidah with chains of transmission (sanad) to be sure what constitutes belief and disbelief.
Tawbah (repentance) is the way out. Recite Astaghfirullah al-Azhim every day at least 100x.