Yes, this happens to me, sometimes during the day, and very often at night. I hear melodies and lyrics that are made up, but someone is singing them in my head. It isn't a bad thing, although it can be distressing when I'm already in a certain type of manic episode where everything is getting me agitated and my senses are heightened. During euphoric mania, I enjoy it though.

I hear jazz, rock, classical...now consistent genre. Sometimes just vocals without any background instruments. It doesn't bother me lately. Occasionally I won't hear vocals, but just melodies. I somewhere read this is also more common in people without BP/mental health conditions than one might think.