Jaiminīya (Talavakāra) Brāhmaṇa 2.252

Knowing thus, having joined his self together in day and night, in half-months, in months, in seasons, in years, in all this, he crosses over that death which is in the heavenly world.
He who knows thus does not die again.
His bones become composed of verses, his flesh composed of sāmans.
Having struck off evil, with his body shaken free, transcending that death, he shakes off his body.
Now these two are the divine and the human Virājs.
Mounted upon these two, this sun burns:
The four quarters, the four intermediate quarters, and these two worlds—
this is the divine Virāj.
Now the human [Virāj]:
Four are the eaters, six are the foods.
The Brahmin, the nobleman, the commoner, and the servant—these are the eaters.
The cow, the horse, the goat, the sheep, rice, and barley—these are the foods.
Mounted upon these two, this sun burns.
There is no heat, no cold; he hungers not, he thirsts not; there is no turning back for him.
Neither does he hunger nor does he thirst, nor is there any turning back for him, who knows thus.

Indeed, as semen does the Udgātṛ pour the sacrificer out when he sings the Bahiṣpavamāna.

He stirs up mind with the seed-bearing verse, breath with the Gāyatrī, eye with the Triṣṭubh, ear with the Jagatī,

speech with the Anuṣṭubh.

He establishes the self with the Paṅkti.

Then, as for this final triplet, that is birth itself.

He brings forth [the sacrificer] through it.

Because this is sung with a sound as it were, with a commotion as it were, therefore embryos are born with a sound as it were, with a commotion as it were.

Regarding this they say: 'It should be sung without sound.'

When [a woman] giving birth experiences severe pain, then she makes a sound.