Yes - there is such a genre as Freethought music. And it transcends genres. Here is a list of Freethought artists I am familiar with. If you know of others, please add them to the list. You can sample each artist’s music on their website.
Markella - former opera star turned Freethought recording artist. http://www.markella.com/
Freethought MC - MC stands for Man of Conscious, he creates hip hop music and is in the studio working on his next album - http://www.reverbnation.com/freethoughtmc
Peace of Rock - poetic rock music from and for free minds - http://peaceofrock.net/
Johnny Hoax - Atheist Rapper - http://www.reverbnation.com/johnnyhoax
Also - here are some other Freethought music and entertainment resources you might like to know about.
Keith Lowell Johnson - Atheist comedian - very funny - http://keithlowelljensen.blogspot.com/
Inspirational Humanist Radio Hour - an hour long show out of NY. Airs Tuesday nights at 10 pm but available on podcast as well - great music and musings. - http://www.radiohive.org/category/shows/ihrh
As I said - these are just a few artists I know about. If you know of others, please let me know!