Dear Roman, Ed, Eugene, Eric and Davide, Thank you all very much indeed for your helpful comments. I've forwarded them all to the friend who asked, and I'll let you know if there is any feedback. Any further thoughts on Vivaldi's concerto will be most welcome.
It is interesting to hear about the mandora being a possible candidate. We discussed this instrument earlier this year in connection with Bach's St John Passion, and I'm beginning to think that there is a lot more to it than some of us might have thought. An archlute in A for music in D major makes a lot of sense. It reminds me of a thread on 13th December 1999 in connection with continuo specified for archlute in sharp keys for music by Dieupart. Lots of food for thought. Best wishes, Stewart.
