Physical Audio has released a public beta of Derailer, a physical modelling system (AudioUnit plugin) with two basic elements: a metal bar that you can strike or bow, and a nonlinear mass/spring connection. This allows you to join two bars together so that vibrations from one create sympathetic resonance in the other. By connecting multiple bars you can create new instruments that have their own unique sound.
There are 37 strike bars, 5 resonators, and up to 81 connections to play with. The adjustable physical parameters and nonlinearity of the connections produce a wide range of tonal variation that reacts to striking velocity or bowing pressure.
A few audio examples here.
Derailer is currently in beta, and is free to use. System requirements: macOS 10.9 ~ 10.12 _
The regular version (download link) of the software requires a 2011-or-later Mac, but the software also exists in a special 'E'-version (download link) which runs on older machines.