Some facts: a string needs two fixed points to be considered as such. We know quite accurately how one of those edges sound, namely the one at the bridge. What is the sound like on the other side?
In this piece there is no electronic modification per se of the sound of the quartet, only amplification. Two contact microphones are attached to each instrument, at two opposite sides of the strings. The amplification is simple: each microphone is mapped directly to one loudspeaker. These two loudspeakers are placed following the same principle as the microphones, at the two extreme sides of the stage. Whenever a sound is picked up by the microphone placed at the bridge of one of the instruments, the sound is projected to the left loudspeaker, sounds picked up by the microphone placed at the neck of the instrument are projected to the right loudspeaker.
At each instant only one of the microphones is audible, like two cameras pointing at the same corner of a room. At moments the switching from one microphone to the other is smooth, sometimes it turns into a sort of thaumatrope, both images merging into one by means of the speed of the cuts.
The same piece is performed at least twice, with a different automation of the amplification each time.