Not having kept close track of this thread I apologize in advance if I am repeating information here.
Please note that my comments are specifically in relation to 17th & 18th century Italian music. With the change in musical style that occurred at the turn of the 17th century performers (and composers) were looking for an instrument with greater volume, which in the case of plucked stringed instruments, meant a larger vibrating soundboard and a correspondingly longer string length in order to accommodate this larger body size. As most on this list know, a gut g string will break at about 69-70 cm (A = 415). When you start using g and a tuned instruments (the norm at the turn of the 17th cent. in Italy) with a fingerboard string length of 76 + cm you have no choice but to tune your first two strings down an octave. While this might seem odd to some, remember that the function of a bass line was dramatically different during the first part of the 17th century than what it was in the 16th century and in the 18th century. It was not necessarily part of a "melodic fabric," it was often not ornate and often functioned as a harmonic fundamental that could easily be transposed up or down an octave without compromising the work in the slightest. Don't misread what I am saying, certainly there are times in early 17th century music when the bass line has an integral melodic function, but much less so than in late 17th/early 18th century music. This corresponds to the fact that number of publications that specify the use of "theorbo" or "chittarone" declines precipitously after 1650. At this point most Italian publications begin to call for an archlute or "liuto" rather than the theorbo or chittarone. At least for me, this means that in 18th century music I usually use an instrument without re-entrant tuning (or just the top string down), and in 17th century music a theorbo with both top strings down the octave. The issue of the re-entrant tuning on a guitar is a very different subject. First it has noting to do with string length, and second it has nothing to do with bass lines...as has been pointed out it has all to do with campanella passages. But what constitutes "re-entrant" on a guitar? only the 5th course up? the 5th & the 4th up? octaves only on the 4th? octaves on 4 & 5? (which Sanz states is the norm in Spain.....is the only tuning ever designated in Spanish sources....and is called for in many Italian sources with campanella passages.....?) Ahhh more food for thought.... R Savino -- To get on or off this list see list information at http://www.cs.dartmouth.edu/~wbc/lute-admin/index.html
