Is it a real Gregorian Chant? Nope. For one - there are no real words in it. Honestly, I don't want a religious exaltation mucking up my fantasy world. So if you're building a historically accurate "Monk Simulator: Year of Our Lord 882!", just move on. The other reason this isn't real is I never learned how to read that notation. There are insufficient sticks for the rhythms in the notation... I know, there is a real convention that you can learn. I just grabbed a few pieces of the sheet music from the 1200s, and guessed at how to do it. Sounds reasonable enough to me! (says the guy who knows virtually nothing about the art)

Gregorian Chant

I'm a composer what writes musics for the peoples! It can be used in videos, or games, or videos games! Bus terminals, day spas, tiger-watching safaris... Anything you would like music for! See my site for attribution requirements.

A chain is only as strong as its weakest link.  

Everything beyond me is a chain.

I will bend all material to my Storm.    

Gregorian Chant

KevinMacLeod