Ulla

The Ulla People had been a very intelligent and technological species. Their technology had overwhelmed them, so they had created a machine to rectify the damage they had caused to their home planet of Xirrinda. The machine was the Rain Of Terror. It reduced them to tribespeople who created thatched houses and kept great paintings to remind them of what they had been and to warn them of the monster they had created.

Their ancestors had also created a machine to deactivate the Rain Of Terror. It was hidden deep within a mountain, in a cavern beyond many endless tunnels. The Doctor helped reactivate it and the creatures were destroyed instantly. (NSA:  Rain Of Terror)

Traditions

 * The Ulla people liked to sing and recite legends.
 * The Doctor had the train carriage fill with drumming as Attar thought back to the stories he'd heard.
 * Singing was used to open a secret door in the tunnels.
 * Singing was used to reactivate the machine that stopped the Rain Of Terror in the end.