Adding a separate midi section using keyboard

I have created a song chord track in Cubase 11 Pro using 4 Halion tracks to play together. I would now like to add a Bass section played on my midi keyboard but when I try and record a midi track when I press the keys the song playing on the chord track goes silent and the notes sound weird. I think it might be the settings I have selected. I am a total beginner.
Tony

Hi and welcome to the forum,

How is the Cord Zack tired to the 4 HALion Instrument tracks, please?