I'm sure there are a number of reasons for this but I'm fooling around with both nectar2 and Antares Harmony Evo...both of which can use midi to generate harmonys from my voice.  I just set each up to go to a submix buss from 2 midi tracks to record them direct (rather than play the track, export the harmony's, then reimport them) and realized I can't record the submix busses...
 
would be nice...
 
Indeed, to have the take lanes and all.... I would be able to explore various midi input harmonies real time 
 
 
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