https://juzek.itch.io/beeps-and-boops
You can figure out which one for what, but I was thinking dadaDEDEdadaDEDE quietly for background,
Choouip for getting friendly ghosts
Buaawaap for when you loose
dukadukadukadua for when the baddies get close
I really like your visuals, and I'm not much of an audio person, but your ghosts are begging for something!