Cool! Yoshimi would be a more logical choice these days maybe, but alas...
If you didn't notice ;) , there is also JackSession now (and Ladish).
Maybe some documentation how to add support for your session stuff to other session managers would be good.
\r
Someone mentioned that after I had already patched ZynAddSubFX. The patch doesn't readily apply to the Yoshimi code, but I'll look into adapting it.
JACK-Session is, from my perspective, far too basic to be useful. And, AFAIK, Ladish is still lacking a robust protocol, currently relying on Unix signals, JACK Session, and LASH to communicate with clients. And, of course, LASH was always inadequate. I first started having issues with SM back in 2008. Not much has actually been accomplished since then to meet the requirements mentioned in my 2008 post (although Ladish does behave better in many important aspects than lashd ever did).
The NSM API is well documented and I think that having support for it in Ladish would be a Good Thing and not incompatible with the project goals, although the user experience may suffer if LASH, JACK Session, etc clients are allowed to mix in an NSM session becuase certain points of consistency could no longer be guaranteed (due to the limitations of those APIs).
That being said, as you can see in the demo, Non-* will come with a fairly fully featured session manager right out of the box if you can live without the Ladish 'rooms' concept.