I'm a self taught upright player, and I get around reasonably well and have ben gigging a couple time a month with a jazz trio. I can't seem to get a grip on the idea of "thumb postion." The idea is that playing above the octave harmonic or so, you use your thumb as a barre or sort of like a capo, in ordeer to make it easier to press the notes down. When I try to do this A: it hurts, B: it doesn't work--I can't hold the strings down effectively with my thumb, and C: I have a harder time playing in this position. It's easier for me to get more on top of the fingerboard than thumb position seems to allow. Am I missing the boat on this? How many of you have trouble with thumb position?