As far as I am concerned it is never acceptable for a regular thread to lock an rt thread for exactly the reason you mention: priority inversion deadlock. You forgot to mention one other method for achieving this communication; System V ipc messages, which i prefer because they don't lock (if used right) and they are simple. See the man pages for msgget, msgsnd, msgrcv. I think that LADSPA plugins can be used as softsynths to good effect. LADSPA hint # 0x2C0 (LADSPA_HINT_DEFAULT_440) allows for a plugin to be pitch controlled. This is not as fancy as other plugin api's but it works and I think we will see more and more use of it. Using a LADSPA plugin as a softsynth requires a decent amount of work on the part of the host: each LADSPA plugin instance is only one voice and polyphony must be handled by the host. However, there are now hosts out there that have the framework to handle this. Steve Harris' lib-rdf is available: http://plugin.org.uk//lrdf/ but i have not used it and can not say anything useful about it. It is used by ardour though. -jacob robbins.....