Hi Jerry,
I love this song! The version I have is off the "King Bee" album that I believe you played on. Is the background harp theme a trill using the 3/4 draw holes? For a while I thought it was hand vibrato (if that is the correct term), but now I don't think so. Also, if I am not mistaken, isn't the same thing happening on "King Bee?"
A secondary question has to do with the way to do such fast trills. Being very right-handed, I find it difficult to do a fast side to side trill without controlling the harp with my right hand. While I guess that's okay, it is hard to maintain a good cup, and, if playing amplified with a mic, even harder. I have been trying to learn to use a head shake instead, and am getting better at that, but for fast, sustained trills, like on "King Bee," I have a tough time maintaining a good rythym with a head shake. My question is whether or not you've seen good harp players do this type of trill (amplified) with their hand rather than their head? I will keep working on the head shake but it is so much easier for me the other way.