Krishna is present in His Name. He is there when we are chanting. Sometimes when we chant, by His mercy, we really feel His presence. We know He is there and the kirtan becomes very wonderful. I experience this in different ways, never quite the same. The Lord in His deity form, Srila Prabhupada, or other spiritual personalities, appear in the mind. Sometimes spiritual feelings arise.
Although Krishna is always there, sometimes we don’t feel His presence. He keeps Himself hidden, and I feel like a stone and the chanting seems empty. Krishna does this so that we will examine our heart and, with greater humility and sincerity, call out to Him. It’s not automatic or mechanical bliss, there is a reciprocation going on. Somehow, we need to chant and hear. But that is our time to be with Krishna and we need to be aware of what is happening in our relationship with the Lord.
If this seems like too much work sometimes, you can always go back to the basic instruction of chanting and hearing, and bringing the mind back to being present with each mantra. This is the basic instruction Srila Prabhupada gives and we don’t have to over think this. Chant with the tongue and hear with the ears. But it is natural that, as the mind settles down and you become absorbed in chanting, devotional feelings come.