Jaiminīya Upaniṣad Brāhmaṇa 3.32.9

3.32.9

tāni vā etāni catvāri sāma prāṇo vāṅ manas svaraḥ
sa eṣa praṇo vācā karoti manonetraḥ
tasya svara eva prajāḥ
prajāvān bhavati ya evaṃ veda /
ṣaṣṭhe 'nuvāke caturthaḥ khaṇḍaḥ //

These four, indeed, are the sāman: breath, speech, mind, sound (svara). This breath acts through speech, guided by the mind. His offspring is sound alone. Possessed of offspring becomes he who knows thus.
Fourth subsection in the sixth anuvāka.