Musical instrument design

It occured to me today that in the sphere of musical instruments, design seems to largely be frozen. The design of the classical instruments has remained static for centuries for example. While electronic generation of sounds and different interfaces for that interaction have taken place there are no real new designs of instruments in the same genre as classical instruments.

Something novel in the strings, brass, woodwind etc. Is it because all ideas are exhausted in this realm?

It doesn't appear to be limited to Western music either; if anything Eastern instruments are even more ancient and again there appears to be a complete lack of new designs or innovation in musical instruments.

I wonder why this is so...