more like single instances of something (just like Ports), rather than the Class/Type style (ie "Voice Pitch Controls") term I'm looking for. to this, I'd think, but I can't remember seeing one... My plugin API has parameters , pins ( similar to ports ) and 'voices'. The relationship is that parameters map to pins, and controllers map to pins. For example: pin 0 - "Master Volume" (parameter, monophonic). Pin 1 - "Note Pitch" (controller, polyphonic, mapped to MIDI Note-On/Pitch). Pin 3 - "Tempo" (monophonic, mapped to host tempo). The host decodes MIDI and maps controllers to pins. The plugin API need not support MIDI at all (yay!), you could migrate to using OSC messages just as easily with no change to your plugin code. The end result is that the plugin API is *very* minimal, 3 functions support most of the GMPI requirements... class IMpPlugin : public IMpUnknown { public: // Processing about to start. Allocate resources here. virtual int32_t MP_STDCALL open() = 0; // Notify plugin of audio buffer address, one pin at a time. Address may change between process() calls. virtual int32_t MP_STDCALL setBuffer( int32_t pinId, float* buffer ) = 0; // Process a time slice. No Return code, must always succeed. virtual void MP_STDCALL process( int32_t count, MpEvent* events ) = 0; }; Jeff