this isn’t complicated, but the current implementation was a deliberate design choice 
letting JF handle note allocation for polyphony meant only using one output for all four tracks, assuming all four are set to JF ouput (which is my primary use case
). the current way seems more flexible, and allows for incidental chords via notes from different tracks overlapping.
i could dm you this change if you want to play around with it, but will likely leave the current implementation in place.
this i’m not sure about, but if everything sounds sync’d… maybe it’s just a rounding difference in displaying the tempo?