PGM's engine is doing a good job with it's own "in house" MIDI following chords, but there is no way (at least that I know of) that you can use your 3rd party MIDI loops or phrases in similar manner > Load a 2,4,8 etc. bar MIDI loop and make it follow your chords.

While Super MIDI tracks are next best thing, if you want tighter control, flexibility and be able to swap sound (synth), there are just not enough of them.

For example I want particular sections for intros, breaks, endings. Basically force BIAB to act as a more traditional hardware arranger instead of trying to cobble sections from existing material, which at times can be a very lengthy and challenging task. With proper MIDI loops that can be achieved quite easily, but they have to follow chords and re-interpret chords if changes are made.

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PGM made an attempt to re-purpose existing MIDI phrases as what is now a MIDI Trk tab in MPT Library. Some of these are usable, but sorting, filtering and overall implementation is very raw at this point in time.