I had this phenomenon a lot when I first started hearing things. I would hear it, I would know there was no physical source- I lived three miles from the next house and every thing inside our home would be off. I could hear that it had words, but I could not make them out.
The first occurrence was the night my roommate (older female ) and I were in the house we rented. She laid down to sleep on a pallet in our living room, and I went to shower. I got in, was showering then kept hearing music super loud. I came out to see what must have her so upset, that she would be blasting music at 1 am. She was sound asleep, and as soon as I opened the bathroom door it stopped.
Eventually I realized I the song I was hearing was one my boyfriend held close to his heart. Coincidence? maybe/maybe not since I didn’t physically hear it until many months later. After the fourth or fifth time I mentioned the type of song, sound, and even some specifics about the guitar and stuff he started playing through his playlist till we found it.
I had originally thought it was from a spirit living in the upstairs of the house.
Funny thing though, I haven’t heard it once since I left him in Washington and arrived in Pennsylvania. I have however heard a different song that sounds like his, only much sadder.
I don’t have an explanation or a verdict or even a cause for you. Only that it might not be as odd as it seems to you atm :).