When using 2 instruments, both using the same plugin, and not using sandboxed plugins, changing either instrument DSSI control will change all instrument DSSI control.
Using sandboxed plugin doesn’t exhibit this behaviour.
That’s indeed weired and not really expected from a plugin, but I think that’s simply how the “Zynaddsubfx DSSI” works. We don’t really have an influence on this as a host.
I’m not too familliar with Zynaddsubfx. Maybe somone which has more experience with it under Linux can help out here with some tips.
to expand on this particular bug, I was the one who committed the DSSI control support in zynaddsubfx and suspected first that my code was at fault.
Each zasfx DSSI instrument is a separate C++ instance (I logged stuff to stderr to make sure that 2 separates instances were created) and renoise sends the dssi control value of the current instrument to every DSSI instances.