There were two kinds of descendants of Pragapati, the Devas and the Asuras. Now the Devas were indeed the younger, the Asuras the elder ones. The Devas, who were struggling in these worlds, said: 'Well, let us overcome the Asuras at the sacrifices (the Gyotishtoma) by means of the udgitha.'

In plain words: The creator had two families of children: the Devas (gods) and the Asuras (demons). The Asuras were older. The Devas were fighting them and decided to win by singing the udgitha, a sacred chant sung during the sacrifice.