When it comes to weird instruments, most tend to be more artistic, rather than functional. Alex Sobolev's "Triolin" is a handmade triple violin that requires three players to work together at once. But that's only half the challenge.
You'll notice that the Triolin doesn't have chin rests. You'll also notice the people holding the Triolin in the photo gallery below are gripping the violins' necks backwards. Add the two together, and you'll quickly realize that players will have to bow the Triolin's strings backwards, too.
Not only does that that sound terribly difficult, but it looks like each violin's scroll (that's the top part of the instrument) rests on each player's shoulder, which doesn't look comfy at all. The Triolin also can't be balanced properly if its players are of different heights, which sucks for shorties who wanna play with taller people (unless they use a stool).
How does the Triolin actually sound? We have no absolutely no idea. You'd probably need three clones of Igor Stravinsky to make this thing work properly.