My friend and colleague Joshua Kosman, who has been the widely esteemed chief music critic of the San Francisco Chronicle for thirty years, is stepping down. In a farewell column, Joshua looks past the near-extinction of classical-music criticism as a profession — an ever-dwindling handful of people in America still have full-time staff jobs in the field — and conveys a characteristically wise and warm message to his audience: "The important thing is to have the conversation, to take music seriously in all its divine glory and human fallibility . . . We listen, we react and then we go in search of the reasons we responded as we did. Did you find the music exciting, boring, incomprehensible, weirdly familiar? Can you try to say why? Congratulations — you’re a music critic." Fortunately, there is no danger of Joshua's voice going silent; it will surely be present in less institutionalized venues. There's a celebration of him tonight at Manny's, in San Francisco.