Concentration or Samadhi the 2nd circle
Morality must be complemented by practicing concentration (samadhi) and wisdom (pragya). Unless a person meditates, morality training will become a burden. Concentrating on the breath will directly connect the individual to the state of mind. Using the breath as a tool is an excellent way which all the enlightened ones have recommended for meditation. There are other subjects that can be used for improving concentration, for example, verbalization (mantra, chanting the name of a deity, positive affirmations, etc.) or visualization (imagining a god, guru, or light).
If we understand the meditation objects deeper, we will realize that the science of mantra is nothing but manipulated rhythms of breath, which will create its own ripple of specific vibrations. Mantra has got little to do with the sound, as most people believe that it is the sound of the mantra which creates the vibration. Even if a person utters a particular mantra with the prescribed rhythm he or she will not be able to produce the same sound as the other person, because the sound depends on various factors and no two persons can have the same sound. It is not that these methods are not useful for meditation. But these methods are generally used for people who have a gross mind. Finally they are also tools used for taming the mind. Chanting a certain mantra repeatedly brings the chaotic mind to focus resulting in a certain state of calm. Similarly for people who have faith in some person or deity, it is easier to use visualization as a tool to tame the mind. But just taming the mind is not the goal of meditation, it is the beginning.
It is recommended that the object of meditation should not be a created or manipulated object. The breath is the purest object, easily available, and always in the reality connected to the state of body as well as the mind. As one starts practicing according to the laws of nature, right concentration will act as a barricade or a boundary and keep the negative defilements from entering, giving a sense of calm and equanimity.