Gayatri fetches Soma from the sky and Vishvavasu steals him. The gods send Vac, who comes back with Soma; the Gandharvas claim her. Both sides woo her: the Gandharvas by reciting the Vedas, the gods by inventing the lute and singing. She goes to the gods. The text calls the choice vain, and explains that the cow for which Soma is bought is Vac.
Soma is among the Gandharvas. Vac herself proposes to be bartered for him because the Gandharvas love women; the gods object that they cannot be without her; she promises to return when needed. Hence one speaks inaudibly after the Soma is bought, until the fire is carried forward.
What is different here:
The plan is Vac's own; there is no theft by Vishvavasu and no contest of recitation and song.
After Gayatri brings Soma, Vishvavasu steals it for three nights. The gods turn Speech into a woman one year old and redeem Soma with her. She becomes a deer and runs from the Gandharvas without coming to the gods. Both call her: the Gandharvas utter a spell, the gods sing, and she goes to the gods. Hence a child speaks at one year and the Soma cow is a year old.
What is different here:
Speech is a one-year-old girl and then a deer; she flees both sides before the singing wins her.
Sources: The Satapatha-Brahmana, tr. Julius Eggeling (Sacred Books of the East 12, 41); Rigveda Brahmanas: the Aitareya and Kausitaki Brahmanas, tr. A. B. Keith (1920); The Veda of the Black Yajus School (Taittiriya Sanhita), tr. A. B. Keith (1914)