As I've mentioned when this has come up before, I tend to whistle a merry tune. It carries a very long way on a country road, and is a much gentler way to alert people to my presence than a bell, which can be taken as aggressive.
I do have bells on a couple of bikes. In particular, my Brompton has a bell integrated into the left shifter. I never use it on purpose, but quite often catch it when changing gear or just moving my hand. Occasionally I've probably confused one or two pedestrians who were just minding their own business. Sorry folks.