Regulations and Censorship is a very important part in the music industry. Nowadays you see a lot of albums with the parental advisory mark on. This is to stop younger people listen to a bad language but other than that mark there isn't a lot of censorship.
If a kid wants to listen to music then its easy for them to go on YouTube and watch a music video with violence or bad language. Some music videos do have an age rating on them where you need to log in to prove you are 18 but this is easy to get around.
But there are occasions where the label record wont accept the music an artist creates and therefor fires them or tries to never release the song to the public. A good example of this is Body Counts "Cop Killer". Ice-T sang the song "Cop Killer" which talked about him killing a cop as this was the time to get payback for all the police brutality against black people. Due to the nature of the song it was never publicly realest but it has been sung at live concerts and can be fount on YouTube.