A Physical Resonator For A Virtual Guitar is a project from Amit Zoran and Pattie Maes at the MIT Media Laboratory. It is an electro- acoustic guitar with a changeable soundboard. By releasing a catch the middle part of the guitar can be popped out. The strings are secured on a tailpiece, so the soundboard can be changed without taking them off. The guitar uses a floating violin style bridge and piezo transducers. I think that this instrument is a great test bed to compare different soundboard materials and bracing styles, as everything else can be held constant while comparing different soundboards.

Zoran and Maes have gone further by measuring the frequency response of their soundboards via the piezo transducers, then using digital signal processing to adjust the output to a desired frequency response.

The original design concept (called reAcoustic eGuitar) had separate changeable resonating chambers for each string. The chambers were to be made of a synthetic material (like carbon fibre), allowing them to smaller than a conventional guitar. The design allows the guitarist to interchange chambers of different sizes or materials to get their perfect sound. Each string had its own bridge connected to its own chamber. The authors go further to suggest that guitarists could share designs for sound chambers, and even make them at home using low-cost rapid prototyping machines (not yet a reality - especially with carbon fibre materials). The futuristic design of the reAcoustic eGuitar looks great, I havn't seen anything like those individual bridges before.

Link: Original Paper for Zorat & Maes Physical Resonator for a Virtual Guitar