I only remember two scenes of this movie.

The first one is that this guy is standing outside on a balcony, he plays a guitar lick very loud with his eletric guitar and someone else, very very far from his house, replies with the same lick. Same thing happens a couple of time during the movie -

And the second one is that at one point a bunch of people get gonorrhoea after having
Unprotected sex -

I know it's not much but, does it ring the bell ?

Possibly Jack Black's "Tenacious D"

Tenacious D in The Pick of Destiny (2006) - IMDb (http://www.imdb.com/title/tt0365830/?ref_=nv_sr_2)