Here's my problem with what you guys are proposing (that audio A>B and MIDI B>A should not be considered feedback): Imagine track A has a VSTi on it, and track B has an audio-to-MIDI plug on it. Now, whenever our VSTi plays a note, it gets sent to B, where it's converted to MIDI, which gets sent to A, which triggers a note, which sends audio to B, where it's converted to MIDI, which gets sent to A... I can't think of a reliable way to allow what you lot are proposing while precluding stuff like this happening - after all, how is Reaper supposed to know when a plugin is capable of producing MIDI output from audio input? Feedback routings are just a bad idea in 99% of cases. Just make extra tracks, and use the track manager to hide those you do not wish to see in arrange view or the mixer.