The Road to Thule, by David R. Lee: A techno-magical dystopian novel set in a flooded world, with songs.
'Souls such as ours bear within them the terrible energies of cosmic fire and ice, the anvils of the giants. We are of the Allfather's brood, and were forged for something greater, something that reality shatters on. You are of that bloodline, Alex, and you will come to know it.'
Exiled from his pleasant life in the heathen Kingdom of Wessex, Alex Tyler embarks on a journey through the flooded British Isles' archipelago of tiny nations, to the far North. There, he is swept up into the power of Thule, masters its secret magical technology and becomes the warlord who will save his people.
As Wessex and the other nations of the British Isles lurch into outright war with monotheist fanatics the Pure Light, the outcome will depend on two strange technologies. The problem is, one of them is deadly for any but a tiny, genetic elite to use, and the other, only Thule knows about.
