There was an interesting article by Eric Walter Hill in Early Music a few years (1993 I think) that addresses the issue of Florentine manuscripts contining intabulated "continuo" accompaniments to late 16th and early 17th century monody.
If i am not mistaken (I am still in Denver playing Handel and do not have a copy of the journal here with me) in his study he found the majority of these intabulations were for a six course lute pitched at A. R Savino -- To get on or off this list see list information at http://www.cs.dartmouth.edu/~wbc/lute-admin/index.html
