few important notes on powerful mantra Om

The essence of all beings is the earth, the essence of the earth is water, the essence of water the plants, the essence of plants man, the essence of man speech, the essence of speech the Rig-veda, the essence of the Rig-veda the Sâma-veda , the essence of the Sâma-veda the udgîtha (which is Om).

The Rik indeed is speech, Sâman is breath, the udgîtha is the syllable Om. Now speech and breath, or Rik and Sâman, form one couple. And that couple is joined together in the syllable Om. When two people come together, they fulfil each other's desire. Thus he who knowing this, meditates on the syllable (Om), the udgîtha, becomes indeed a fulfiller of desires.

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https://www.sacred-texts.com/hin/sbe01/sbe01022.htm#fn_71

When the sun rises it sings as Udgâtri for the sake of all creatures. When it rises it destroys the fear of darkness. He who knows this, is able to destroy the fear of darkness (ignorance).

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 pratyâsvara 1 (reflected sound). Therefore let a man meditate on the udgîtha (Om) as this and that (as breath and as sun).

https://www.sacred-texts.com/hin/sbe01/sbe01024.htm