Hi! 
I really like the Fusion Sampler workflow, but I don’t know how to control it in-game so that certain inputs trigger note on/off events, i.e. not based on a pre-existing MIDI sequence. The game I’m making has cases where the same “instrument” should be playing a sequence sometimes, and letting you play the notes directly.
Even if I create a MIDIStream input in MetaSounds, it seems like there’s no interface for it in Blueprints, so I’ve tried hacking it like so: Trigger To Music Transport → Metronome MIDI Clock Generator with its tempo set to 0.0 → MIDI Pulse Generator whose Note Number and Velocity I set before triggering Play (note off = velocity 0.0); and triggering Play on the Trigger To Music Transport node for each note “event”, but I lose polyphony, quite unsurprisingly. I’ve also tried leaving the Velocity alone and triggering different combinations of the Trigger To Music Transport inputs for note on/off, same story.
Is there anything I’m missing? Of course I could try and replicate what the Fusion Sampler does directly in MetaSounds for this, but it would be very tedious, plus I don’t think there’s any way to read and break down a Fusion Patch Asset directly, to check note ranges per wave file etc.
Thanks in advance! 
Just as I was continuing my research: 
it’s just lucky that I’ve just found the solution right after posting the problem)