Ohmigod Kat you are testing my memory now! But I do remember that they would not be full-blown songs, more like the chorus of one song, followed perhaps by the chorus of another.There were no real "Halloween" songs that I remember. Current chart songs would be just as likely to be sung as traditional. I do have a vague memory of singing "Molly Malone" at Halloween once, (hardly traditional Scottish I know) but that may have been as a party piece, rather than at somebody's door.
I am sure the memories will trickle back ..........
Murray