“I used to fall asleep in the stacks near the Philip K. Dick novels, and when I woke up at 4 or 5 in the morning Michael and I would just talk about life,” said Alex Brook Lynn, 37, a journalist. “We once discussed what a conversation between James Cagney and John Cassavetes would have sounded like.”

“One of the great joys of living in New York has been bringing people to Brazenhead,” said Isaac Butler, 40, a critic who is writing a book about the history of method acting. “The experience only got richer when you passed it on. Brazenhead was the fantasy of New York you came here to get, but it was only here. The myth of New York still existed in this place with this man.”

A bell was occasionally rung to silence the crowd, and guests offered remembrances. One of them was the novelist Jonathan Lethem, who worked for Mr. Seidenberg as a teenager in Brooklyn, accepting books as payment, and later wrote him into his novels.

“I walked into Michael’s Atlantic Avenue shop in 1978,” Mr. Lethem said. “I kind of just decided it was going to be my life to be Michael’s right hand for as long as I could be, and it changed my life in a lot of different ways. I think I might be Patient Zero.” Then he looked to the crowd and added, “You all self-selected to be part of this tribe.”