The only reason folk singing (other than in fests & clubs) is not a strong tradition is because the majority of people don't sing other than singing along to pop songs.
Once you get into the habit of singing in the family and with friends it becomes a living thing again. And once you get over the initial self-conciousness, singing becomes a natural thing & the songs get propagated.
Its often fear of appearing odd or inappropriate that stops people singing. I've found family & friends more encouraging and appreciative than I ever expected.
What I'm trying to get around to saying is that just because we have, as a nation, lost the links - doesn't mean we can't rebuild the chain. If music is important o us then we need to have the courage of our convictions.
Harmony singing is wonderful when you get a hall full of varied voices of strangers singing harmonies on the fly to the familiar chorus melodies. Best not over-used though - some songs are best naked and unadorned.