I, too, am interested in Just Intonation for playback (as well as dynamic tuning systems like Hermode tuning). I suppose part of the question is how tuning ends up being implemented in playback. E.g. if a LUA script can (eventually) attach VST Note Expression tuning information (and/or MIDI pitch bend) to the playback data, I’d be very happy. Of course, explicit support for non-EDOs (i.e. rational divisions of octaves) would be most welcome, too! 