wtkJams KE has the ability to restrict users from selecting the exact same song as another singer in the play list.
To change the
Duplicate Songs setting, go to the Settings app of your iOS device. Scroll down and select
wtkJams KE settings page, tap
Allow Duplicate Songs? to toggle the setting.
Exit the Settings app and return to
wktJams KE and the
Duplicate Songs settings will have been changed.