I wouldn’t call the solution a filter because the qchord works fine with General Midi Synths (like SoundCanvas) but not so great on other non GM synths. If I recall the qchord generates C notes in 3 octaves and then pitchbends those notes to the correct pitch for each guitar string. Unfortunately it takes floating point math to convert the pitchbend data into midi notes which I’m not sure is possible with midihub. Here is a Pure Data implementation:

I finally figured out what is going on. There is actually nothing wrong with the Q-Chord midi implementation. Your external synth just needs to have these requirements:

1) your synth needs to be multi-timbral with at least 3 instrument slots (set to midi ch 14, 15, 16)
2) the three instruments patches must be set to MONO
3) pitch bend on each patch needs to be set to 12 semi-tones

I have it working on my Nord G2 modular but most Nord keyboards should work because they are generally multi-timbral with 4 patch slots. I have yet to test this on my Nord Lead 1 but the docs show where to set the pitch bend, so I’m sure it will work. I’ll include an image from my Nord G2 editor to show you what I tested this on. It plays everything perfectly especially if you use the “length” pipe in midihub because sometimes the notes don’t sustain long enough.