It's illegal to claim the copyrighted material of others.
Jack is a bedroom music producer who wants to grow in popularity.
Jack wants to be paid for a great song.
Jack practices hard at production, creates his masterpiece, and sells it on his website.
Jack finds an obscure song from a popular artist and sells it as his own.
Jack is proud of himself for creating a brilliant original work.
The original artist decides to sue Jack from the use of the music to make a profit.