Hi, To put it clear, I am not talking about sympathetic resonances. That is a problem on electric guitars, at high volume. But you also see acoustic guitarists dampening when using a plectrum.
I also do not have a 6course lute so I can't test any of this. But what is MAYBE the case, is that plectrum playing lutenists did use the thumb for dampening strings they did not want to sound and that this hand position just stayed for some time until more courses made it impossible. Our problem is that we are trying to reconstruct the start of a story where we know what happened at the end. We have a few bits of information, but we will always be infleunced by what we know (or at least we know more) about later lute playing. There is something quite distateful about early lutenists using what we consider to be "bad" technique. But if a plectrum lutenist (or maybe a strumming "finger" lutenist)wanted to play a chord such as C or Eb or D, which did not use the lowest string, the safest way to play these chords is to damp the lowest course. This would allow him to be a bit more free in his strumming. It may also be that even when playing single notes that they sometimes used quite wild wide strokes to get more volume of for effect and dampening the other strings stopped anything sounding that should not. Also interesting is how long 6 course lutes remained popular. I think that a 7th course tuned a tone lower was possible much earlier than it became widespread. Maybe they just liked those fat necks so they could put their thumbs in that strange position. But as I said, I don't have a 6 course and rarely play early 16th century music, so everything I say is just wild conjecture. best wishes Mark -- To get on or off this list see list information at http://www.cs.dartmouth.edu/~wbc/lute-admin/index.html