Guessing here take for it for what its worth, but if the song lasts at least 6sec. of play, you pay royalties, etc., I think that excludes public service or for the public good. Even so, this is an area you need to be aware of or you will be educated the hard way. Pay now or later, Geeezzzz,(bite tongue) a good time for a lawyer to get involved or google away for possible answers. Don't let all that YouTube stuff fool ya, if something becomes popular, a legal letter can be sent. Pay or get the release.
An example, TV shows pay for the slightness play of song tunes and/or old TV commercials(jingles) and a check is sent to the author or owner of the piece. Now, you know why the "screen writers guild" wants more of that piece of action for their works.
tada -----Willy 