I don't believe in Nembutsu, Requiem or praying at the death-beds. When I look at a dying or a cold, stiff, dead person I only wonder if this person had practiced enough during his living days or not. If he had, then all the praying for him would make no difference. His soul would move up regardless, just like oil on water. But had he not practiced, his would sink like a stone thrown into a pond. People pray and chant (Nembutsu) at the death-bed more as a formality than any practical purpose. You go ask all highly ranked monks and respected scholars and see if they can point out any part in any sutta mentioning monks praying to help to lift a person's soul after he had already died.

In my opinion, there is only one special situation and that is when a person is still alive but very near death; where some guidance may be provided through words from Buddha and saints. This is the situation of visiting at a sick-bed, different from the scene of crowds gathering around a death-bed and praying loud and long in the hope of somehow rescue the dead person's karma. The person is either already dead or in a terminal coma (dying state of not knowing, not hearing) - yet people keep crowding around him, praying from one sutta after another, some even in Pali language! In all the suttas I have read, there is not one mention of monks visiting and praying to a dead or comatose person.

Buddha, Sariputta, Moggallana or Ananda all may have visited and provided guidance to a few persons who were very ill but who could still hear, understand and reason. The sick may have been asked succinctly (and not subjected to long chanting of a winding sutta):

"Are you coping with the suffering? Any regret or fear?"

"It is better to have a sick body than a sick mind. Mind sickness is from sadness or worries caused by the many troubling terrifying emotions of the body."

"Do you see me as a body form? Or does body form appear in me?"

Once there was a monk who was so enraptured with the Buddha that he never wanted to be out of his sight. When this monk became sick one day and was unable to see the Buddha, he became despondent. The other monks asked him why he was so unhappy. He explained that he was depressed because he could not see the Buddha, who then came to visit the sick monk and said to him: "What do you see in this vile form? There is nothing to see in that. Whoever sees me, sees the Dhamma, whoever sees Dhamma, sees me. "