Theft is an assumption of property rights  Theft is taking something from someone who is the rightful owner without their permission. It doesn’t matter if the rightful owner keeps an original version or not. If you are downloading music from an unofficial source, you are stealing it: you can start listening to that song, without the permission of the original owner. The only way you can get the right to listen to that song is via a legal transaction from which the rights owner can make a profit