These sets have been mixed using tracks that I have downloaded for free through Jamendo. Jamendo is a Creative Commons music site dedicated to showcasing CC music from around the world. You name it, you can find it, be that glitch core infused folk, or reggae death metal! I have been blessed to find some of my favorite artist here.
I use a piece of software called Djay by Algoriddim which you can find here. I have found it easy to use and would recommend it