Music can be shared under open source principles that allow remixing, for instance under matching Creative Commons licenses and on platforms like Soundcloud. It is common sense, that a release as open source makes the piece more attractive, it can gain through word-of-mouth advertising and can become more popular than non-free pieces.
Does anyone had measured the positive effect on popularity for music? Or, if such a thing for music don't exist, how is it with other forms of work? How useful is opening up the work as a tool for marketing?