Apparently the simplicity of the tune is belied by the fact that it is a pretty difficult piece to play - Mr. Williams makes it look effortless - as you'd expect.
Yep, Andy Hughes, it sure is a real tough nut to play. I had the music for it, written for two guitars, and that was ok. But I also had a version written for 1 guitar, and it was just mad! Though it IS possible, as a friend of mine once did it (albeit slowly) as a party piece. Beautiful, simple, intricate piece of music.
Cavatina is a musical term, originally a short song of simple character, without a second strain or any repetition of the air. It is now frequently applied to a simple melodious air, as distinguished from a brilliant aria, recitative, etcetera, and often forms part of a large movement or scena in oratorio or opera.