actually, now that I think of it, I do agree. It was the whole run that came with it that amazed me. :) I'm not from Korea, but I believe it is a song that is traditional (my friend showed me)
YES I love Sohyang! I can't believe not many people know her O.O Her performances on Immortal Song are always amazing (just like this one). Go check out her cover of Michael Bolton's Lean On Me cause it's awesome (she even won on that episode with Mr Bolton himself there so what more is there to say)
And it is a traditional song, but there are many variations.