Sutra 3.3.9

9. And (this is) appropriate, on account of the extension.

Since the praṇava, which is a part of the udgītha, is introduced as the subject of meditation in the first prapāṭhaka of the Chāndogya, and extends over the later vidyās also, it is appropriate to assume that also in the clause 'the gods took the udgītha'—which stands in the middle—the term udgītha denotes the praṇava. Expressions such as 'the cloth is burned' show that frequently the whole denotes the part.—The conclusion from all this is that in the Chāndogya the object of meditation is constituted by the praṇava—there termed udgītha—viewed under the form of prāṇa; while in the Vājasaneyaka the term udgītha denotes the whole udgītha, and the object of meditation is he who produces the udgītha, i.e. the udgātṛ, viewed under the form of prāṇa. And this proves that the two vidyās are separate.—Here terminates the adhikaraṇa of 'difference.'