Listening to a CD in a store, is occasionally rendered difficult by Karaoke types who are unaware that they are singing quite loudly to whatever it is that they are listening to, on the headphones "next door".

I am not sure what it was, as the chap seemed to only know the chorus, and, (unless the tune itself was particularly tuneless), there was a larger than "acceptable" number of keyless notes issuing from his mouth.
Turning up the volume on my headset was of no use.
I'll go back later and try again. Maybe I'll encounter a delightful barbershop quartet gathered around a single headphone, singing in dulcet harmony. One never knows...

Rest assured, if you delight in singing along to that which you are listening to - in store, where none of us have the benefit of knowing the rest of the music - I am not, repeat, not a musical producer on the lookout for an undiscovered musical talent to take advantage of.

Your talents are quite quite quite quite quite safe from me.
;)