The thing I find extremely puzzling in the 'awful lot of paintings' you mention is that, for late 16th and almost all 17th century examples, there is a nearly uniform depiction of a thumb-out technique, which is also described clearly in written sources. With one exception, nearly all our notable baroque lutenists of today use a thumb-under technique. This even applies to a lutenist I've seen in a recent video who is described as never having played renaissance lute. What gives? Why don't baroque lutenists today use what is an unquestionably obvious historical technique?
Thumb under/in was the best way to make a clean break from unworkable classical guitar technique in the early days of the lute revival at the point when lutes built on real & proper historic principles made such a break a necessity; not merely a stylistic indulgence. At the same time, the harsh, but twangy sound quality of the strings available- particularly the thin, overspun basses- could only be adequately tamed by rounder, softer strokes resulting from the thumb-in hand position, also played closer to the rose than the bridge. One anachronism cancelling out the other, as it were. Speaking as a lifetime player who made that exact transition, back in the 1970's, by practicing it fanatically five hours or so daily, I can tell you that one does not give up or radically change such a hard won goal lightly. (No historical record of any of the original players making the difficult switch from thumb under to thumb out, and then going back to the prior technique) But, when I obtained a 10 course lute some years later, I was indeed bothered by the injunctions of Nicholas Vallet- whose music I had fallen in love with- Stobaus, etc., and the overwhelming iconographical evidence. I slowly began exploring historic thumb out/over, nothing at all like classical guitar. It was only in 2004 that I felt comfortable enough to use historic thumb-out in performance, but having given up music as a profession I had more time to experiment and fewer high pressure gigs requiring unconsciously rock-solid technical security. Also, gut and more gut-like bass strings made such a refinement sensible and rewarding. Not that my videos are anything to write home about, but you can see and maybe hear the differences between my RH techniques on the 6 course lute vs. the vihuela. They will be more obvious if I ever record on the archlute or d-minor Baroque lute. http://www.vimeo.com/user814372/videos Apologies for some harsh sounds, much work still to do if I live long enough. Dan -- To get on or off this list see list information at http://www.cs.dartmouth.edu/~wbc/lute-admin/index.html