Guitar-piece

Often in the movie, there is an elderly man playng an acoustic guitar, and he does it really well! After the citizens of the village and troops have the fiesta-party together, the man plays a piece of music on the guitar. It's kinda split into two parts. First part being pretty up-beat and happy, the other half being more mellow and sad. He repeats it a few times.
Where this piece originally from?? Is it an old piece of music.
The reason why I ask is, I have a cd with an old thrash metal band called Aeturnus, and the album is "From Blackest Darkness" (yeah, what a title), and they play the exact same piece of music as an outro to one of their songs! The cd is from 1996!

Prepare to evacuate soul.