Hello Pob,
have you perhaps tried the Melodyne editor Trial since you installed Melodyne essential, and played with its
Pitch Background options? If so, please try trashing the Melodyne preferences file
com.celemony.Melodyne singletrack.plist (with a capital M!) in
Users/<your name>/Library/Preferences. Does this already make a difference?
If this doesn’t help, please contact our
support team. They might need to ask you for further info.