I had an old chemistry teacher (research chemist with more letters after his name than you’ve had hot dinners) who in a random lecture, was talking about a load of newly fangled polymers: That by creating a lattice/crystalline structure with these polymers, you could trap metal oxides (coloured compounds) inside. And by altering frequencies of AC current passing through the polymer (these were electrical conducting plastics, hence the new fangledness!), you could alter the structure minutely and hence allow light to reach the different metal oxides...hence allowing an image to be produced in a similar way to an old fashioned cathode ray TV (combinations of magenta, cyan and yellow) this would allow for a wafer thin, incredibly strong and flexible screen with a full colour image that would have an instant refresh rate.
Now.
I was thinking. With carbon fibre guitars, you can get pretty much any tone you want (with that graphite zinginess of course...) by altering the density of weave of the fibres, akin to the differing densities and grain-widths of different woods. But how about actually changing the tone with a click of a switch? Line 6 did it with amp modelling wizardry and some snazzy pickup electronics...but apply the structure-changing-polymer idea to a change in width of a material’s “grain”...right? Now set up a guitar body made out of strips of this polymer stuff and by passing different frequencies of AC current through each strip, you can replicate ANY material tone out there...and the guitar would made out of plastic (so it can now be any number of colours, and very lightweight)
You could set it up so that individual sections of the guitar (neck, different parts of the body, fretboard and who knows what else...) could have different frequencies passing through them...hence allowing the guitar to retain ANY tone possible.
Now let's further this even more.
There's a pickup manufacturer who uses LEDs focused on the strings, with LDRs picking up the light to create a sound signal. This means the strings don't need to be made of metal - they can be made of this polymer stuff too (it's flexible remember?). Allowing you to instantly change the tension, frequency response and texture of a string....as well as the frequency response of individual sections of the guitar itself.
In a nutshell: a guitar that can make any sound because it consists of a material that can replicate ANY frequency response whatsoever
The problems I can think of with this though are that you’d need a stupid amount of power to make this possible...like every strip of this polymer would need a high voltage/low current flowing through it (like a plasma ball) and you’d need AC signal generators on every single bit you wanted to have a different frequency...and they’d need to be rather small.
And also I may have made numerous offences to english linguistics in this post, I was typing in rather a hurry
this was thought up when I was walking home with a grade-8-cello-playing mathematician who was considering the idea of carbon fibre cellos (lightweight...defined tone and virtually any tone the customer wants...hummm, there's a business plan)
But other than that! What do you think folks?
The ultimate synth instrument.... 
