Yes I steal tunes now and again without noticing. Then I spend days wandering around trying to remember where I've heard the tune before. Once I know where I lifted it from I'm happier because I can see the differences or what changes I can make in it. I bug all my acquaintances by asking them "Have you heard this tune before? Where have you heard this?" They usually answer as well as they can. There is only one guy who bugs me by always saying "Yes you plagiarized that one." But he can never tell where from. I've stopped asking him.