The Reverberation of Sound, or Dratenjur (Tibetan: སྒྲ་ཐལ་འགྱུར, Wylie: sgra thal 'gyur), is considered to be the root tantra of the seventeen tantras of the Menngagde approach to Dzogchen.
These tantras are found in the Nyingma Gyubum (Tibetan: རྙིང་མ་རྒྱུད་འབུམ, Wylie: rnying ma rgyud 'bum), volumes 9 and 10, folio numbers 143-159 of the edition edited by Dilgo Khyentse (Thimpu, Bhutan, 1973) of the gting skyes dgon pa byang manuscript.
Generally in the Buddhadharma, sound as an object of discourse and a created 'phenomenon' (Sanskrit: dharma) is 'impermanent' (Sanskrit: anitya) because of being a product, it is 'conditioned' (Sanskrit: samskṛta-dharma). Philosophical 'views' (Sanskrit: drishti) or 'conclusions' (Sanskrit: siddhanta) on the nature of sound are very important in all Dharmic Traditions, traditions of Dharma and dharma schools of thought. The nature of sound is of particular importance to the early Buddhadharma as it was one of the ways Shakyamuni differentiated his teachings from the prevailing views of his time which held the sounds of the Vedas to be eternally authoritative. As a general rule, Buddhist systems emphasize that sounds do not of their own accord inherently express their meanings but are arbitrary conventions, socially determined and understood by consensus. Historically, Shakyamuni was reactionary to the status of the 'revealed authority' (Sanskrit: apauruṣeya) of the Vedas the ritual incantations and sounds of which were held as permanent and eternal. In the Vedic system, the sound and sign of the syllable or visible mantra was held to be none-other than what it communicated. This is understood in Linguistics and Semiotic Theory as motivated language or appropriated language where the signifier 'appropriated' the essence or quality of the signified. For example, the sound, sign and signified were all the same in essence. Early Buddhardharma as a general rule ostensibly rejected such reified 'essences' (Sanskrit: svabhāva) as it was such views that supported the notion of the 'self' (Sanskrit: atman) which in turn supported the rigidity of the Varnashrama dharma social system of caste that Shakyamuni challenged (Williams 1980, 1981). But this is not always the case in the Buddhadharma as the sound in the title of this tantra denotes the immutable, unconditioned, uncreated, 'primordial sound' (nada). It is in this notion that the Tantra of the Vajrayana and Mantrayana and that of Sanatana Dharma are in accord.