These may have been answered before somewhere, but...please, please could someone help me out with this questions...

I am a white european guy who has long hair, is long hair on men a problem in Iran culturally, or are there laws involved with it, is it simple yes/no, a certain length, a question of style? I can find out nothing specific, only the odd news report, which is no way to find out real information, so I thought this was a good place to ask and get a straight answer on this. I would not like to arrive in iran and then get bad looks or offend anyone just because of my hair, I'd rather know ahead of time, and maybe have a trim if it is the only way!

Also, what is the situation with music? I play guitar, so it would be normal for me to get work maybe playing in small places, earn a little extra money. Is this allowed in public, certain instruments only, are licenses very important? How would this kind of thing be percieved, does it happen a lot, only in cities perhaps?
One of the reasons I am interested in the country is for the music, learning the oud etc, so the question of whether a westerner is allowed to perform or play music is interesting to me.

many thanks