It is also the Brahmanaspati (lord of the Yajur-Veda). Speech is Brahman (Yajur), and the vital breath is its lord (pati). Therefore it is called Brahmanaspati.

Yajur Veda, Brihadaranyaka Upanishad I, III-The Prana: Its Glories and Redeeming Power, 21

Prana is Saman, too. Speech is, verily, sa and this (prana) is ama. Saman (the chant of the Sama-Veda) is known by that name because it is sa (speech) and ama (prana). Or because it (prana) is equal (sama) to a white ant, equal to a mosquito, equal to an elephant, equal to these three worlds, nay, equal to this universe; therefore it (prana) is indeed the Sama-Veda. He who knows this vital breath to be such attains union with it or lives in the same world with it.

Yajur Veda, Brihadaranyaka Upanishad I, III-The Prana: Its Glories and Redeeming Power, 22

And it is also the Udgitha. The vital breath is verily ut, for by the vital breath all this universe is upheld (uttabdha); and speech is githa (song). And because it is ut and githa, therefore it is Udgitha.

Yajur Veda, Brihadaranyaka Upanishad I, III-The Prana: Its Glories and Redeeming Power, 23

Regarding this there is also the following anecdote: Brahmadatta, the great-grandson of Chikitana, while drinking king [soma], said: Let this soma strike off my head if I say that the ayasya angirasa chanted the Udgitha through any other means than this vital breath and speech. Surely he chanted through speech and the vital breath.

Yajur Veda, Brihadaranyaka Upanishad I, III-The Prana: Its Glories and Redeeming Power, 24

He who knows the wealth of this saman (Vital breath) obtains wealth. Tone, indeed, is its wealth. Therefore let one who is going to perform the sacrificial work as a priest desire that his voice may have a good tone and let him perform the sacrifice through that voice with a good tone. Therefore people desire to see at a sacrifice a priest with a good voice, like one who has wealth. He who thus knows what is the wealth of the saman obtains wealth.

Yajur Veda, Brihadaranyaka Upanishad I, III-The Prana: Its Glories and Redeeming Power, 25