To me that was indicative of how important the kirtan is that Prabhupada, even though he was trying to write so many books and do so many things, but he still just sat down for an hour, he would just listen to the kirtan and nod his head. But he was completely happy. Everybody was dancing and he was swaying his head, and he looked very immersed in some kind of deep reverie.
Last Days in London- Srila Prabhupada immersed and absorbed in Kirtan
Adikarta das: He would sit on the chair in front of the Deities, and the kirtan went on for a long time. I remember Bhagavan, he was leading, but they were singing that tune, Hare Krishna, Hare Krishna. And so Prabhupada was sitting there watching and he was completely happy, it seemed, just listening to the kirtan.
Reference: Following Srila Prabhupada-A Chronological Series by Adikarta Dasa