Alright, this is how I see it. We must not be unequally yolked
to the things of this world. Not just specifically to music, but to
anything that would cause us to sin. While the actual listening of
this music may not specifically be a sin, anything we consume, will
eventually have an effect on you. Like for me, I was heavily into
hardcore gangsta and underground rap for most of my sec sch times,
I ended up often very angry and hateful. In all honesty, I do not
see any reason to see why the melody and sounds eg. heavy guitars
and drumming are sinful, but such songs content is all about
hopelessness and anger eg. A7X's Bat country....
Some artists have even started using the styles of music to
glorify god.
P.O.D (nu-metal)
http://www.youtube.com/watch?v=a2_pC_LqCMo
try and look at the lyrics to this song, it's one of my
faves
Living sacrifice (Metal)
http://www.youtube.com/watch?v=mxo6HV1r43Y