First of all, let's get this straight. Music is a property, and people own their piece of work. Therefore, if you do not get the consent of the owner of the music or the audio, you don't have the legal right to distribute that music to get profit. However, the owner should sue the person who used the music without permission to legally start a case. Therefore, we can say that you won't get in trouble with law forces for downloading a song to listen to on your MP3 player, mobile device, or computer.