Originally posted by Axl_Rose
... i just question how necessary it is to know what mode your playing, when all that matters is what sounds good!

If figuring it out bothers you , then it isn't necessary at all.

I heard too that Slash has got nothing to do with music theory , and he used some modes and harmonic minor scale probably without even knowing what are these called.

To write good music, all you have to know is when does it sound right or wrong.