Looking to identify a guitar piece?

The main melody goes something like

B B B B a g g f# e e g B E E E E D C C B a a B C B C B D# C B B a g g f# e f# f# f# f# g f# e e e e,

where I am using lower case letters to denote note below the starting pitch (so the entire melody fits inside one octave from e to E). All notes are nearly equal in length, though I've heard it with some flexibility in tempo (e.g. slowing down prior to the high E's and at the first B C).

Thanks in advance, and my apologies if this falls closer to folk music than classical (I'm not sure enough about the source of the melody to know in which category to post it).