I felt like reviving this thread.
The 3rd Bridge Guitar:
The name is pretty straightfoward, these are guitars with 3rd bridges, lying on the neck. This concept began with musicians simply taking a regular guitar and then applying an object (like a screwdriver or a drumstick) underneath the strings and on the neck, creating a third bridge, giving the guitar brand new tones that resemble bells and chimes. Lee Renaldo of Sonic Youth is notable for doing this. Eventually though luthiers began making their own custom 3rd bridge guitars. Glenn Branca and Fred Frith (from the band Henry Cow) are examples of musicians who have made their own 3rd bridge guitars.
The one shown in the picture is a custom made instrument called the Moodswinger, though its not really a guitar as much as its a zither. It has no frets and lacks a conventional guitar neck, in addition the pick ups and electronics are built into the neck, rather than the body. It was designed by Dutch luthier Yuri Landman especially for the Indie band Liars.
Weither people use a custom made 3rd bridge guitar or make their own by just using a screwdriver, this techinqiue has become rather popular with avant garde and alternative rock musicians. Fred Frith, Sonic Youth, Liars and Slint being the most notable examples.
YouTube - Sonic Youth-Bull in the heather
Bull in the Heather by Sonic Youth, making use of the screwdriver technique.
YouTube - Good morning, captain - Slint
Another example, this time by Slint.
YouTube - Fred Frith - Hello Music
Something to listen to when you're tripping balls.
Liars – Leather Prowler – Listen free at Last.fm
Brief sample of the Moodswinger.