Is i mutar if its a non-Jewish artist?
Gezel Akum is just as forbidden as stealing from a Jew.
As for your other questions, ask a Rav.
Personally, I ask myself the following questions:
1. If it was me, would I like it? I get annoyed when people steal my pictures (and yes, it happens) and use them without payment and attribution. Since I don’t like it when it’s done to me, I don’t do it to others.
2. Are you so hard up for the cost of the music that you can’t do the right thing and compensate the artist whose music you obviously find pleasing enough to consume?
The Wolf