I agree that it is too subjective and that you draw your own lines. I'm with McGrath that much depends on the performance - I think of, say, Bascom Lunsford's lovely rendition of 'In the Shadow of the Pines'. There is truth too in G.K. Chesterton's comment [I can't recall where I read it in his writings] to the effect that sentimentality is simply having feelings and not troubling to invent a new way of expressing them.

--Stewie.