If you want to do the right thing and get permission to use copyright material it's not easy for something like this. The copyright agencies don't seem to have caught up with current technology.

I was thinking of putting my cover version of something on Soundcloud and enquired with PRS/MCPS if there was an appropriate licence. If I was putting it on a CD this could be done for a very modest cost. All they could offer was a licence which seems to be aimed at someone setting up a music download service, at a quite disproportionate cost. I'm left with the choice of either only putting up public domain and own copyright material or taking a chance. It's hardly surprising that most people do the latter.