Mantras are only endowed with transformative energy if given in initiation (dīkṣa) from the mouth of the Expert. It is not so much suitable pronunciation, but alternatively the power with which the mantra is endowed that offers it reworking capability. Mantra obtained its optimum advancement in Hindu and Buddhist Tantras, https://mahavidya26059.blogminds.com/a-review-of-beej-mantra-33817143