Nembutsu vs mantras and dharanis related with Amida

Amida Buddha image
at the altar of Amidaji temple

Question: Can we chant various mantras or dharanis associated with Amida Buddha/Amitabha from the esoteric schools instead of His Name? 

Answer: In His Primal Vow (18th Vow) Amida Buddha exclusively mentioned the saying of His Name (Nembutsu), so we only say His Name. As no mantras or dharanis are mentioned there, we do not recite them. From the myriads of practices, related or not related with Him, Amida chose His Name, so we must be in accord with His wish. I explained this aspect in more detail here (click to read).

Being a Buddha, He knows better why He only chose the Nembutsu in His Primal Vow, so we should not busy our minds with something that goes beyond our limited capacities, but follow His command and say His Name exclusively. 

Question: Then what do you think is the purpose of the mantras and dharanis associated with Amida?

Answer: Those mantras and dharanis, but also various other practices associated with Amida in other schools may help those who wish to be reborn in His Pure Land but don't have the faith of the Primal Vow, and so they are still attached in one way or another, to their personal power. Those are provisional practices related with the 19th Vow which leads, if followed seriously, to birth in the borderland of the Pure Land. I explained in detail the causes of birth in the borderland here (click to read).

Only the Nembutsu of total faith in Amida Buddha's Power which is mentioned in the Primal Vow (18th Vow) leads to birth in the fulfilled land of the Pure Land ("center" of the Pure Land) where we immediately attain perfect Enlightenment. This is the teaching of Shinran and we must not deviate from it. As Jodo Shinshu is the school of the Primal Vow we must exclusively say the Nembutsu.

There is also another difference between Nembutsu and various mantras which may be associated with Amida. A mantra should be said in a special state of mind or in a special way to emit a certain sound, while Nembutsu does not require that. A mantra is received with empowerment in order to be effective, which is again, not the case of Nembutsu. So, there is a great difference between the two. Nembutsu is not even a recitation (although you can recite it), but a simple saying, as the sound does not matter.