Whenever I'm on my travels, either here in Blighty or sur le continent, I've whipped out a little G blues harp in the churches we visit (which have been many) and played Amazing Grace. The acoustic is always very forgiving. I haven't managed it in a cathedral yet. One never wishes to offend. It's a simple and perfect little tune. I played it at my dad's funeral and, just last summer, at a little ashes burial ceremony.