After quite a bit of fiddling, I got a waveguide mesh working. It’s a physical model of a drum head, basically lots of bidirectional, single sample delays connected in a triangular mesh to form a hexagon. [update: now a second extern is in there that tessellates a circle instead].
It sounds pretty good already, next plan is to play with different ways of exciting it.
The supercollider plugin, together with some haskell (hsc) code for testing it, is downloadable here.
[update: native sclang code and classes included now too]
[another update: new version with patch from Dan Stowell, it uses less CPU now]