Mantras are only endowed with transformative ability if provided in initiation (dīkṣa) with the mouth of the guru. It's not much suitable pronunciation, but instead the ability with which the mantra is endowed that provides it reworking ability. Cundī dhāraṇī or mantra also first appeared during the Kāraṇḍavyūhasūtra: namaḥ saptānāṃ https://www.instagram.com/tantramantraaurvigyaan/