http://www.wakingtimes.com/2017/09/08/hindu-priest-explains-subconscious-mind-can-reprogrammed/
“As a spiritual tool, monks of the eastern traditions have been using mantras since time immemorial, most recognizably along with prayer beads. The value of this type of meditation is well-understood by practitioners, although, difficult to quantify. It offers a simple but powerful means of creating the emergence of desired positive outcomes in personality, habits, beliefs and emotions…
Speaking on how this process works, Hindu priest Dandapāni explains how mantras are similar to affirmations in how they work to reprogram the subconscious mind. In an interview with Brian Rose of London Real, Dandapāni answers the question of why the simple concentrated repetition of sound can so powerfully bring about positive changes in personal behavior.
“You can say they are prayer beads, but they’re actually more like affirmation or mantra beads. So, we use these to actually program our subconscious. So as we chant on each bead, we chant an affirmation. I am happy, or I’m confident. And we repeat the same chant over and over again, and there are 108 beads… one chant over and over again.”
There is more to it than just saying a phrase 108 times, however, and as he explains, three ingredients are necessary: “Concise choice of positive words, clear visualization, and a corresponding feeling.” …
Regarding a corresponding feeling, he explains how feeling is emotion and emotion is energy, quoting the late Nikola Tesla.
“He [Tesla] had this beautiful saying which kind of encapsulates Hindu philosophy really well. He said that, ‘to find the secrets of the universe, think in terms of energy, frequency and vibration.’ Everything is made up of energy that’s vibrating at its own frequency. What we believe is that if your subconscious is filled with patterns that are vibrating at a certain frequency… and if you can go into your subconscious and create a pattern, infuse it with energy that’s vibrating at a certain frequency, you can attract things of a similar nature to it.”
The combined effect of intentionally applying sound, visualization and emotion to create positive change can override the contents of the subconscious mind.”
CosmicMind 
The transcendental nature of the sounds involved are also important. The Maha Mantra (Hare Krishna) has such transcendental sounds and can change one’s consciousness.