Hi - my name is XXXXX XXXXX I'm an Intellectual Property litigation attorney. Thanks for your question.
LEGALLY speaking, it is illegal to use a copyrighted work for personal gain without getting permission from the owner of the copyright. Thus, this would likely be illegal. Here's a good link you could read: http://www.nolo.com/legal-encyclopedia/question-using-portion-of-song-without-permission-28112.html
Obviously, the likelihood of actually getting caught doing this and even being sued is slim because the cost of pursuing a legal claim probably outweighs the money damages that could result, BUT that doesn't mean it's legal and it certainly doesn't mean that you won't get sued; however, the odds are low.
That said, you can likely get a license to use the song for a nominal fee, and then you won't have to worry about getting sued over the issue. You can contact the US Copyright Office or visit the website and look up the song to see who the copyright owner is; then you can contact the owner about getting a license.
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