Thank you for that answer, David. Thinking about what you said, I see now that I was not thinking clearly about how one tunes a 10-course lute. I was thinking that one could tune the 7th course as D, and then just add the bass tunings for courses 8, 9, and 10 however they're commonly tuned. In such an instance, one would just ignore the courses 8, 9, and 10. But I see that - by having to find the notes assigned to the 7th course on different lower bass courses - a great complication is added!
I really should have thought of this, since I do tune the 7th course of my 8 course instrument to F, with the 8th course being D. I have been considering reversing them, and tuning the 7th to D, and the 8th to F. But it's easier, I'm sure, to reach down and strike the bottom course, than it is to reach down and distinguish the 7th from the 8th course. I'm rather looking forward to the arrival of the 7 course instrument I have on order! Ned -- To get on or off this list see list information at http://www.cs.dartmouth.edu/~wbc/lute-admin/index.html