Any Guitar player, of which I happily admit to being, that is worth his salt, has at one point or another, either played the infamous riff in this song or at least has tried to figure it out. I must confess, I’ve played the riff, the whole song, is another story.
Anyway, Here is one of my favorite songs by Deep Purple. Notice the funny looking people in the crowd at this show.. heh, those were the days! 
By the way, if you have a good sound system with your computer, this would be good time to TURN IT UP! 