I was recently watching a video of Jack Sanders playing and discussing his baroque guitar modeled on a Stradivarius. One of the comments asked a question I've also wondered about - of the five courses, why is the top course only a single string? I guessed that there were multiple reasons for this (e.g. the historical difficulty of producing identical strings of such a narrow diameter might present tuning difficulties; the melody would more often be played on the top string, so it would sound with greater clarity with only a single string - likewise you could utilize rest-stroke more easily with a single string, which might be used to increase the volume (or accent) the melody line) - but really, this is all speculation on my part.
So - my questions - does anyone have a more definitive answer for why the highest course on a five course baroque guitar is often a single string? Finally, when and why did the highest course become known as the "chanterelle?" Is the same true for lutes and other precursors to the early guitar?
Thanks in advance for any insights!