Download and install:

1. http://vmpk.sourceforge.net/#Download
2. https://www.tobias-erichsen.de/software/loopmidi.html

On loopMIDI:

1. Check the + in the Setup tab to create a new port

On vmpk:

1. Edit → MIDI Connections
2. Uncheck “Enable MIDI input”
3. Under Output midi connection select “loopMidi port”

On AudioPluginHost:

1. Options → Change Audio Device settings
2. Check “loopMidi Port” in Active midi inputs