Not much actually. As a language music doesn't use words, so it is very difficult to write a political piece of music for example. It's easy enough to come up with a political song, and the knowledge of keys and so forth can make the music sound angry.
Music is also about what is appreciated by the public. The South censored blues, jazz and rock 'n roll not by legislation but by preaching it was all the Devil's music.
The only song I can think of that was illegally censored (on radio, although not on the album) was the song "Four Dead in Ohio." This came out as a single right after the slayings at Kent State, and it was yanked off the radio as fast as possible. But no one was prosecuted. The song was urging violent revolution to do away with the criminal Nixon administration. I for one would have joined such a revolution had it broken out.
