Khandogya-Upanishad: First Prapathaka, Third Khanda
2. This (the breath in the mouth) and that (the sun) are the same. This is hot and that is hot. This they call svara (sound), and that they call pratyasvara (reflected sound). Therefore let a man meditate on the udgitha (Om) as this and that (as breath and as sun).
3. Then let a man meditate on the udgitha (Om) as vyana indeed. If we breathe up, that is prâna, the up-breathing. If we breathe down, that is apana, the down-breathing. The combination of prâna and apana is vyana, back-breathing or holding in of the breath. This vyana is speech. Therefore when we utter speech, we neither breathe up nor down.
4. Speech is Rik, and therefore when a man utters a Rik verse he neither breathes up nor down.
Rik is Saman, and therefore when a man utters a Saman verse he neither breathes up nor down.
Saman is udgitha, and therefore when a man sings (the udgitha, Om) he neither breathes up nor down.
5. And other works also which require strength, such as the production of fire by rubbing, running a race, stringing a strong bow, are performed without breathing up or down. Therefore let a man meditate on the udgitha (Om) as vyana.
6. Let a man meditate on the syllables of the udgitha, i.e. of the word udgitha. Ut is breath (prâna), for by means of breath a man rises (uttishthati). Gi is speech, for speeches are called girah. Tha is food, for by means of food all subsists (sthita).
7. Ut is heaven, gi the sky, tha the earth. Ut is the sun, gi the air, tha the fire. Ut is the Sama-veda, gi the Yagur-veda, tha the Rig-veda. Speech yields the milk, which is the milk of speech itself, to him who thus knowing meditates on those syllables of the name of udgitha, he becomes rich in food and able to eat food.
8. Next follows the fulfilment of prayers. Let a man thus meditate on the Upasaranas, i.e. the objects which have to be approached by meditation: Let him (the Udgatri) quickly reflect on the Saman with which he is going to praise;
9. Let him quickly reflect on the Rik in which that Saman occurs; on the Rishi (poet) by whom it was seen or composed; on the Devata (object) which he is going to praise;
10. On the metre in which he is going to praise; on the tune with which he is going to sing for himself;
11. On the quarter of the world which he is going to praise. Lastly, having approached himself (his name, family, &c.) by meditation, let him sing the hymn of praise, reflecting on his desire, and avoiding all mistakes in pronunciation, &c. Quickly will the desire be then fulfilled to him, for the sake of which he may have offered his hymn of praise, yea, for which he may have offered his hymn of praise.