In my research I've been able to find plenty of sites that provide royalty-free music available for purchase. But most of these tend to provide a single audio file with every instrument track already blended and mixed together. I'm more interested in the dynamic music route, and would want to download a bundle of audio files (one for bass, one for kick, etc) and in my game I can just bring them in and out based off of what's going on. When things are quiet just have the bass line repeating and when things get chaotic the full piece is going. Obviously each track would need to be on the same beat and designed to work well with each other part. Is there any place that such multitrack loops could purchased? Thanks.