What "technically" happens when we chant Nam Myoho Renge Kyo? I have been chanting Nam Myoho Renge Kyo (daimoku - Nichiren Daishonin's Buddhism) for about 4.5 years. I also regularly attend Soka Gakkai International (SGI) meetings. I have experienced a lot of benefits from the practice. 

But, I have been unable to understand what  technically  happens when we chant. I have read in some of the texts that we create a good karma when we chant or some of the questions here answered that the "act" of chanting leads us to the path of enlightenment. 

But, being a Physics student, I am interested in knowing what exactly happens when we chant. For example- when I chant, I generate sound energy. Now that energy would have some temporal variation as the words "Nam" , "Myoho" etc. would have different sounds but the ratio of amplitudes and frequencies would be almost equal for each person. 

I would be happy if someone can give a technical explanation of what exactly happens when we chant.
The simple explanation is that you are practicing mindful concentration. The latter threefold division of concentration required in the Noble Eightfold Path. Whether you are doing sitting meditation, chanting sutras, calling the name of the Buddhas or Bodhisattvas, or chanting mantras, or even following the monastic discipline Vinaya as a monk. You can't simply concentrate on anything though, importantly it must be Right Mindfulness that is skillful.


  Abandoning the wrong factors of the path "One is mindful to abandon
  wrong view &amp; to enter &amp; remain in right view: This is one's right
  mindfulness...
  
  "One is mindful to abandon wrong resolve &amp; to enter &amp; remain in right
  resolve: This is one's right mindfulness...
  
  "One is mindful to abandon wrong speech &amp; to enter &amp; remain in right
  speech: This is one's right mindfulness...
  
  "One is mindful to abandon wrong action &amp; to enter &amp; remain in right
  action: This is one's right mindfulness...
  
  "One is mindful to abandon wrong livelihood &amp; to enter &amp; remain in
  right livelihood: This is one's right mindfulness..."
  
  — MN 117


Chanting holy names is within this criteria, as with Myoho Renge Kyo -the Sublime Dharma of Lotus Sutra, as they do not promote bad unskillful thoughts and encourage positive reverential emotions. (With the added possibility of divine intervention..) The practice of the Noble Eightfold Path is said to lead to liberation from mental afflictions by the purification of mind, speech and action.

As exactly how the exact mechanics of this works, I can't say for certain, but it does work. Abandoning negative thoughts does wonder for the mind and body. At certain level of concentration you enter what is called the Jhana/Chan/Zen where feelings of bliss and peace arise, and is also a state where you can make many realizations. This is certainly possible through chanting.