I heard this haunting song about 20 years ago on an American celtic radio program. the chorus went "fal la dee da di do, fal la dee da der o, fal la dee da di dee da di dee da der o" . multiple women singing a capella in celtic irish. the name of the group could have been maccala or something close, also could have been the name of the song. have never been able to track it down and I've spent many hours.