The law is different in many countries. In Australia, I tried to get a song licensed for a short film. I had to go through the red tape bull shit.
I had to tell them all this stuff like, how long I wanted the song to be played for, where it was going to be shown, was I asking for money to see my short film etc etc.
For example:
Work: I'm So Tired (Eskimo Joe)
> Copyright: 100% MMP
> Project: Short Film
> Media: Non-theatrical Film Festivals
> Territory: Australia only
> Term: In perpetuity
> Duration: Whole track
> Publishing Fee: AUD$300 + GST
Since I was showing mine at a film festival, I had to get permission from the record company. Even though I wasn't going to be getting any money from it.
So, if you make something and just share it around with family etc, it shouldn't be too bad. If you were going to publicily release it on the Internet, and they found out about it you could get into a lot of trouble (they threatened to sue me because I said I changed my mind about the song. I hadn't even signed any of the papers yet so it wasn't mine).
Then again.. the net is a big place