3rd bridge

The timbre created with this technique is close to that of gamelan instruments like the bonang and similar Indonesian types of pitched gongs.

[3] On harmonic positions the created multiphonic tone is consonant and increases in volume and sustain because of the reciprocal string resonance.

[5] In the 1930s, Harry Partch experimented with this technique on an instrument he called a Kithara that had movable glass rods.

From the late 1970s, Glenn Branca adopted Partch's theory and used amplified string tables for some of his symphonies.

[6] After being trained in the Branca orchestra, Sonic Youth applied their own guitars with screwdrivers, mainly in their early years.

"Nails" (2004) by Kaki King uses a third bridge set over the 16th fret and the technique has also been used by Fred Frith and Keith Rowe in addition to Branca, Moore, and Ranaldo.

The extended technique involves bowing the instrument on the afterlength, the short length of string behind the bridge.

Another example is found in Ferde Grofé’s Grand Canyon Suite where bowing behind the bridge in a violin cadenza represents a donkey’s braying.

Yuri Landman's Home Swinger , 12 string 3rd bridge zither
Landman's 2006 Moodswinger , a 12 string overtone zither .
Different possible shapes of a third bridge: "a common six-sided pencil [4mm contact], a round dowel [more focused contact], and an L-shaped bracket [even more fine]." The pencil creates, "a damping effect and also prevents energy from transferring across the bridge to the opposing string segment," with the dowel, "resulting in greater sustain and cross-string resonance," and the bracket, "offers even more sustain than a [round] dowel." [ 1 ]
3rd bridge preparation, the front and the back tone are in a reciprocal relationship and known as the bi-tone [ 1 ]