What constitutes rock music?

I was reading the other thread about whether 'rock and roll' music is evil. I had a different question. I have not formed a stance yet on the first question, but if I did decide that I shouldn't listen to it, how do I tell what is rock and roll or not? I figured this should be in a different thread because this is a separate question, applying more to those who DO believe it is evil:

Is decided by the tone of the voice?
Is it decided by the instruments used?
Do the lyrics have any relevance? (ie Is Christian rock still evil?)
Is it possible that there are some hymns which have a tune that really stir up my flesh that I should not listen to?
Does contemporary music count as rock music?

Richard Baxter said regarding instruments that there cannot be a forbidding of any instrument. A beautiful instrument that stirs up the flesh still cannot stir more than the most beautiful instrument of all - the human voice.

I really am stirring over these questions (I'm not sure yet about the question of rock music, whether it's lawful or not) and would like to hear from those who believe that rock music is evil - how do you determine if a song is rock or not?

God bless

Speaking for myself only, I avoid most music where the singer has a bad or rebelious attitude, whether in the song or in their life.
As a teenager I listened to an American sermon on rock and roll music. The preacher stated that the term "rock and roll" meant two people (teenagers) having sex in a car, and that was its origin. On the sermon was other stuff, including subliminal messages within songs, some worshipping Satan. It was quite weird stuff.
What I have found is that seeking the Lord Jesus and listening to the word has had most influence on the music I listen to.

Somebody once told me Jesus is the music maker!

"rebellious attitude" - that's a great way of putting it and something to look out for.