All I can think of is to suggest that you find some tunes that were originally secular, but have now become known as "churchy", and then write your own words to them. I think the problem in finding them is that atheists are more likely to be diverse, and less likely to come together in bunches to sing that sort of thing than members of religious groups.What do you want to say? Our humanists in Britain are most notable for writing scathing letters to the papers slagging off the more ridiculous positions of the religious. (Church School bans Harry Potter, for example.) We seldom see what they do believe about human behaviour.

Second thoughts - try the French Revolution - or other writings of that period.

Penny