It's funny that people like to attack Rap music for the "message" Rap music sends out. But glorify people like Johnny Cash who recorded a song called 'Folsom Prison Blues"...Let's take a look at some of the lyrics of what is considered to be a "Classic"........." Well I shot a man in Reno.....Just to watch him die" (loud cheers from the audience).
The context of violence in songs like Johnny Cash's opposed to a lot of the "violent" songs of today is different. When you listen to a Cash song, you sense that he(or his character in the song) knew that what he did was wrong and often time in the song paid the consequences.
From his first album under Rick Rubin, the song Delia sings about how if he had not shot her he would have made her his wife and the first shot didn't kill her but the second round did. But later in the song he speaks to the jailor, so we know that he is paying the price for his mistake. We sense the anquish and regret in his voice.
A lot of songs today seem to want to justify the violence used. They rationalize the actions taken as doing nothing wrong and as the only course available. Thus it glorifys the violence and mayhem portrayed in the music.
All that aside though, a lot of hardliner JWs or elders would want to discourage you from listening to Johnny Cash either due to the violence in his music or because he sang gospel from time to time or because of his relationship with Billy Graham.