Free Advertising

Free songs lure customers to your free EP's, your free EP's lure your customers to get to know you better, they get to know you and if they like you they will spend money on seeing you live, buying your shirt, owning your albums you have for sale. And if the free song did none of the above, it is likely they weren't going to be a consumer of yours anyway. Think of releasing songs for free as free advertising. Not to mention that if someone continues to enjoy music that you continue to give them at some point many feel they should reciprocate what you have given them. They will pay to see shows of yours, they will get you t-shirt when they come. They will tell their friends to check you out which will be easy for them to do because they know that their friends can try your music for free.