One of the first columns I ever wrote for Engadget was about Triple Neck Guitars, which are normally played by heavy metal guitarists with curly perms and an enthusiasm for lengthy solos. Now, straight outta the Mathematics department of a Canadian university, comes the Tritare: A guitar with three necks, but only six strings.
Last week, at the Acoustical Society of America's 151st meeting in Providence, RI, Sophie Léger of the Department of Mathematics and Statistics, Université de Moncton, Canada, presented a paper on "A New Family of Stringed Musical Instruments".
She's one of the inventors of the Tritare. It has triple-ended strings - one string goes up the fretted neck, and the other two resonate on the second, and third, fretless necks (which the guitar is standing on in this picture). You play it roughly like a normal guitar, with the two necks down to your right.
Obviously, the interesting bit is the sound, and this page contains several samples, which are amazing. Presumably they're uneffected, but sound alternately like bells or reverb-covered 'Paris Texas' slide guitar.
The Canadial professors are trying to market the Tritare as a product -- there's a homepage at Tritare.com, but absent are prices or availability. They're also experimenting with networks of strings, which at the moment are more at the clanking and atonal end of things.
Of course, if three necks doesn't sound hardcore enough, you could always build a double body guitar.