Hey PAY!
The answer to your question about free licenses depends on how you understand a license. What do you want to do ? protect the work or give rights to your users ?
If you see the license as a way to protect the code itself (the music in this particular case); then there is no way the BY-SA is ‘more free’ than the BY-NC-SA.
However, some people (me among them) think licenses are meant to give rights to users. With this idea, the BY-SA is far ‘more free’ than the BY-NC-SA; because the former allows derivatives works not allowed by the latter. Following with this argument you come to the conclusion that the BY is the ‘most free’ among the CreativeCommons licenses.
Of course thats only my opinion and since IANAL I might be totally off.
Cheers,
Ferdy