They drive me crackers. I have a default tune that goes round and round from morning till night - 'Yesterday'. I wouldn't mind if it was the original version which I love (or I did!), but it's a kind of ridiculous stylised 'poppy' version that my head seems to have made up just to annoy me. It includes various notes from the instrumental backing, equally popified.
I try to download another song - any other song - into my head, but before long, Yesterday has wormed its way back in with a vengeance. Aagghh
.
I have thought of having hypnotherapy to remove it 