Has the engine had a recent cambelt change?
Sounds exactly like mine, and I did a belt change a few months ago - all genuine parts.
It was previously silent on the old timing belt parts. You can't over or under tension the belt as the tensioner is idiot proof, so it's probably just the rubber belt making a noise as VW are constantly changing suppliers, so the rubber compound might be slightly different.
I wouldn't worry about it mate, it's a normal sound.