References regarding mechanical chanting:
1) Revival of the dormant affection or love of Godhead does not depend on the mechanical system of hearing and chanting, but it solely and wholly depends on the causeless mercy of the Lord. When the Lord is fully satisfied with the sincere efforts of the devotee, He may endow him with His loving transcendental service. SB1.7.6
2) Mechanical chanting is not as powerful as chanting of the holy name without offenses. Sri Caitanya-caritamrta Ädi-lilä 10.43
3) Devotee(1): (reading question) “What are your views about silent meditation on one’s, in one’s own self, and this japa, gäyatri-mantra?”
Prabhupäda: Yes. Simply by mechanical japa, we’ll not be ha… We have to hear from the Sästra what is self. Of course, those who are actually following the rules and regulation of gäyatré-mantra, they’ll be, gradually come to the spiritual understanding. But not as official chanting. That will not help. “Because I have got gäyatri-mantra, oh, om-burble bura burra…” (makes sound) Finish. Not like that. Don’t cheat yourself. Try to understand. BG Lecture 2.22, 11/26/72
4) Devotee (3): Srila Prabhupäda, if after finishing one’s sixteen rounds of the mahä-mantra is it all right to…
Prabhupäda: It is not finished. If you have got time, if you haven’t got to do anything else, you can continue, (laughter) sixteen hundred. It is not mechanical: “Now I have finished sixteen rounds, that’s all.” Why sixteen rounds? You (not) chant sixteen hundred rounds. That is minimum, because you cannot concentrate your mind in chanting, you have no attachment for chanting, that is a regulative principle. You must finish this. Otherwise, those who are actually attached to the Hare Krsna maha-mantra, that Haridäsa Thäkura, they are chanting whole day and night. But you cannot imitate that. Your mind is not fixed up. Therefore it is minimum sixteen rounds. Not that “Because minimum sixteen, I cannot chant more.” Why not more? You can chant more, more. Chicago July 4, 1974
5) So we must be purely chanting. But we should not be disappointed. Even impure… Therefore we must have fixed chanting process. Because we are not in the pure stage. Therefore, by force… Just like a boy in the school. We had this training in our childhood school. Our teacher would ask me, “You write ten pages, handwriting.” So that means practicing ten pages, my handwriting will be set up. So even if we do not follow sixteen rounds, where is the question of chanting Hare Krsna? So don’t be artificial; don’t be, I mean to say, a showbottle. Be real thing. And that is wanted. If you want real benefit of spiritual life, don’t be showbottle. Do you know showbottle? The medical shop, a big bottle. It is full of water only. And color is red or blue or something like. But the real medicine does not require… (aside:) No, not now. Real medicine does not require a showbottle. A small… If one can chant purified offenseless, once krsna-näma, he is free from all material bondage. Once only. Eka krsna näme yata päpa haya, päpé haya tata päpa kari baro nähi(?) SB 1.16.26-30, January 23, 1974
6) Now, when you chant Hare Krsna, if we chant mechanically, then the effect is different. I have already given you ten kinds of offenses there are in chanting Hare Krsna. So mechanical way of chanting is also another offense. So offenseless chanting… Of course in the beginning, neophytes, we are apt to commit so many offenses. But we should be careful that the chanting should be offenseless. Then we shall realize that Krsna is present by His name. He is present. You’ll realize and you’ll have the same effect as you expect by meeting Krsna personally. You can see Krsna and you can hear Krsna. Because Krsna is absolute, there is no difference between seeing and hearing. That is the absolute sense. People give more stress on the eye: “Oh, can you show me Krsna?” Oh, can’t you hear Krsna? Why do you give…? This is also one sense, that is also another sense. Do you think by seeing you’ll understand everything? You are seeing so many things daily. Do you understand? So this is all foolishness, that “Can you show me?” Now we have got so many senses. So perception through any sense, because He is absolute, the same effect. Either you see Him personally or you hear Him. Rather, hearing is better because by seeing you cannot understand Krsna. When Krsna is present, all people saw Him, but they could not understand Krsna. But one who heard of Krsna even five thousand years after, just like we are hearing, we can understand Krsna as far as possible. So hearing is most important thing. You’ll find in the Thirteenth Chapter, çruti paräyaëa. Çruti paräyaëa. Çruti paräyaëa means one who is very much eager to hear about Krsna, he’s a very nice qualified man. So hearing is very important thing than seeing or touching or smelling. Hearing is very… Hearing is the, is so important. When all other senses are not acting, sleeping, no other sense is acting, as soon as telephone bell is called, you get up. No other sense will act. So hearing is so perfect. Therefore according to Vedic principle this hearing is very important thing. Hearing. And one who is very much eager to hear about Krsna is very expert, because hearing is knowledge.
7) So if we hear Krsna, about Krsna, His name, His fame, then Krsna is present before us. Srila Prabhupada lecture New York 1/16/67
8) As soon as I began to meditate upon the lotus feet of the Personality of Godhead with my mind transformed in transcendental love, tears rolled down my eyes, and without delay the Personality of Godhead Sri Krsna appeared on the lotus of my heart.
O Vyäsadeva, at that time, being exceedingly overpowered by feelings of happiness, every part of my body became separately enlivened. Being absorbed in an ocean of ecstasy, I could not see both myself and the Lord.
The transcendental form of the Lord, as it is, satisfies the mind’s desire and at once erases all mental incongruities. Upon losing that form, I suddenly got up, being perturbed, as is usual when one loses that which is desirable.
I desired to see again that transcendental form of the Lord, but despite my attempts to concentrate upon the heart with eagerness to view the form again, I could not see Him any more, and thus dissatisfied, I was very much aggrieved.
There is no mechanical process to see the form of the Lord. It completely depends on the causeless mercy of the Lord. We cannot demand the Lord to be present before our vision, just as we cannot demand the sun to rise whenever we like. The sun rises out of his own accord; so also the Lord is pleased to be present out of His causeless mercy. One should simply await the opportune moment and go on discharging his prescribed duty in devotional service of the Lord. Närada Muni thought that the Lord could be seen again by the same mechanical process which was successful in the first attempt, but in spite of his utmost endeavor he could not make the second attempt successful. The Lord is completely independent of all obligations. He can simply be bound up by the tie of unalloyed devotion. Nor is He visible or perceivable by our material senses. When He pleases, being satisfied with the sincere attempt of devotional service depending completely on the mercy of the Lord, then He may be seen out of His own accord. SB 1.6.16-19