Royalty-free music may sound like it’s free to use, but some royalty-free tracks may require you to pay a one-time fee to obtain the work. The term "royalty-free" means you don't need to pay royalties, which is a fee you pay the creator every time you use their work. If you have the budget, you can purchase the rights to use royalty-free music. Otherwise, music with a Creative Commons license will do just fine.