I have one of these:
It's a
vielle - often referred to as a
waisted vielle, a fidel, or various other terms. It was the primary instrument used for "artistic" music from the C13th to the C16th. Technological improvements (a lighter and more resonant body, thinner strings, and perhaps a higher bridge?) were made to the instrument during the C16th, as it mutated gradually into the
lira da braccio. Although the basic idea then developed onwards (in Cremona) into what we'd recognise as a modern violin, many more things changed -including more robust strings, a lighter body made of carved component parts (my
vielle has a body carved from one piece of wood), and a much "bigger" sound.
We mainly use my vielle for medieval music - Machaut, Landini, Dufay, Binchois. I say "we" advisedly (before Mr H comes in like a ton of bricks offtopic as usual) since I loan my instrument out to a better player than I (a professional violist) for these performances, while I migrate onto a recorder or cornamuse, by way of providing some element of variety of timbre for the audience. Most of this repertoire is 3-part, and we perform it one-to-a-part - vielle, cornamuse/recorder, and voice. Of course, audiences sated with the luxury of a modern large symphonty orchestra may find this all very small-scale and lacking in "brilliance" for their tastes... but we've performed a few concerts of Dufay and Landini quite successfully.
Mine isn't the model illustrated - nor did I pay that rather naughty price for it :)) In fact mine is a prototype made by a modern instrument-builder, which he was willing to sell rather cheaply, before he began making them on a commercial basis. Nor does mine have the
bourdon string - but it's not present in all medieval illustrations, and appears to have been a matter of choice. I find it rather a nuisance in polyphonic music (I've got a
crwth which has one, and it becomes annoying very quickly - to the extent that I almost never use the instrument) and I'm quite happy not to have it there :) We have used the vielle and crwth together to play the lower lines of Machaut ballades (I took the drone string off) - but they sound rather similar, and I personally prefer to have a mixture of timbres... although there is really no evidence for this either way. Composers of this period didn't specify the instruments used... and in fact the choice was left up to the players themselves, with a number of different options being both possible and acceptable. Landini himself played the portative organ - an instrument which was played with the right hand only, while the left hand pumped the bellows, and was thus effectively a monophonic instrument.