This might be off-topic, but I'm about to pick up a 7-string violin. I played violin and viola for more than 10 years back in the day, but my shoulder didn't like it...
Anyway, it'll be coming in the next few days and I'll give you my impressions of it. Hopefully I can adjust my technique or hold it differently so it doesn't get too painful -- it seems a shame to waste all the background I had with violin and I might actually be able to get some usable tones out of that thing.
They say the tuning should be E F C G D A E, but I'm not quite sure why they have it that way at the low end. I'm going to try to make it F C G D A E B (regular violin tuning + two fifths down + one up) and might need a source to get B strings. I'm thinking a really thin guitar string might work, as it's smaller in diameter than a violin E string.
Anyone else wants one, I think a company runs them every so often on ebay. I have no idea how the quality is, but it's a really extended range so might be useful in a band with extended-range madness already there