Don’t worry. You have a condition called musical ear. It’s basically one part of your brain doing something your consciousness is not wanting to be aware of but the music continuous on its own merry way without your permission or desire. Same with the the loud hum and other assorted phantom noises. The low pitched hum is a difficult sound I find because it’s hard to mask it or over ride it with other sounds. The music itself can be instrumental or voices as in a choir. Unfortunately for me the tunes repeat constantly and it gets very very boring. I can have an impact by saying to myself I will ignore this or change the tune which requires effort and doesn’t make the noise go away. Musical ear I believe is a form of tinnitus, for hich at this point science has no cure.. The good news is that you are not crazy, just ear damaged. I would suggest that you pursue the angle of accident incurred in your car accident if you have not already done so just to see whether something physical can be addressed in terms of offering relief. You should also be tested for an acoustic neuroma (tumour pressing on auditory system). You need to see an Ear, nose and throat doctor as well as an audiologist. The American Tinnitus Association is helpful. I think they have an audiologist who will answer your questions at no cost to yourself. Good luck on your journey forward looking for solutions and finding a sympathetic physician who has an “ear » for your problems.