व्याप्तेश्च समञ्जसम् ॥ ९ ॥
vyāpteśca samañjasam || 9 ||
vyāpteḥ—Because (Om) extends (over the whole of the Vedas); ca—and; samañjasam—is appropriate.
9. And because (Om) extends (over the whole of the Vedas), (to specialize it by the term ‘Udgitha’) is appropriate.
Since ‘Om’ is common to all the Vedas we have to understand which particular ‘Om’ is to be meditated upon. By specifying that the ‘Om’ which is a part of the Udgitha is to be meditated upon, we learn that it is the ‘Om’ of the Sama-Veda. “Let one meditate on the syllable ‘Om’ (of) the Udgitha” (Chh. 1. 1. 1).