We want to add MIDI control to one of our existing plug-ins, which is currently just an Audio Unit with JucePlugin_AUMainType set to kAudioUnitType_Effect. We've successfully been able to route midi to the plug-in by changing the type to kAudioUnitType_MusicEffect, but as a result, when reopening a session saved with an older version of the plug-in, the host complains that it can't find the plug-in (because the types are different). We're able to load new instances of the MIDI-enabled plug-in, but it doesn't maintain session compatibility.
Has anyone experienced this before, or know of a workaround for maintaining session compatibiliy with a different main type for an Audio Unit? Or is there another way to get MIDI input into the plug-in, without changing the type?