There are a few very old songs still in circulation. Apart from Trireme Goodnight, which I've mentioned before, there was the hymn sung by the Ancient Egyptian Pharaoah who tried to convert the polytheistic empire to monotheism. Their god was the sun, which they named Aten (hence Tut-ankh-amun's original name, which was Tut-ankh-aten), and this was sung to greet his rising, and continued to be popular into modern times:

The Sun, as God, is Aten,
Hip-hip-hip hooray!
The Sun, as God, is Aten,
And he's coming out to play!