If you purchased the music within ITunes form apple, then there is (I believe) a problem in that Apple add Digital Rites Management (DRM) stuff into their supplied music which makes it difficult to move to any other platform (Apple locks you in to just using their devices/systems).
I believe there may be a way of stripping the DRM off your music. Others on this forum may be able to advise how to do but it is, I fear, not going to be easy.
Fred