What PHJim meant to write was:

This is what I think of as Completely parallel harmony. It's hard to tell who is singing lead and who is singing harmony.
Geenwood Side-o - Ian & Sylvia

My own comment:
All in perfect fifths, and sounding fairly idiomatic to me. Each of the two sings one verse solo in the respective "key".

(Some singers at the other end of expertise involuntarily sing a fifth apart, the intention being the same as for "normal singers" to sing an octave apart, i.e. to suit different voice ranges. Very interesting stuff for music psychology, and for conjectures about the origins of European polyphony.)

Pip, was that the kind of music you had in mind?