I’m not sure that’s clear (or right!)
You should have two tracks as in my post above.
Track 1: A MIDI track, with the chord part on it. Being sent to the Blue Arp VST Instrument (which is created in the VST Instruments rack).
Track 2: A VST Soft synth, whose MIDI input is from the Blue Arp VST Instrument. Its monitor should be on.
That should work when you press play.
It sounds to me from your description that you have the BlueArp track feeding back into itself (you say its input is the Blue Arp MIDI out).