Late August and early September: the light shifts, even in Southern California. The sunlight is almost subliminally tinted with a faint amber as if in re-creation of an old daguerreotype, lending the world a certain historic quality. Never perceiving myself as nostalgic, I am nonetheless inclined to think of the past now; after all, at the moment I have more of it than I do ­future.

It is the new school year that comes to mind. Freshman year in Westchester, Illinois, 1964, Saint ­Joseph’s Catholic School for Boys, with your hosts, the Christian Brothers (occasional appearances by certain Franciscan and Jesuit priests). It is freshman orientation, and one Brother Crispin (or Crispian, ­I’ve forgotten which), is addressing the incoming student body of mostly 13-year-olds.

“I know how you boys have spent the summer. Oh, yes! You think I ­don’t? Every chance you got you were writhing up and down, mother naked on your pillows, eh?” Brother ­C’s balding dome caught the auditorium ceiling lights and winked at some one hundred or more of us as if in code for some otherwise ineffable secret of the ­flesh.

“Spilling your seed with the godless glee of Onan! Humping, your taut, athletic buttocks glistening with beads of perspiration.” But it was Brother ­C’s pate and temples glistening with sweat, the brother grimacing as if in spasm. Silence echoed around the gymnasium for several heartbeats before the good ­brother’s microphone fed back and roused his stunned audience. “Well,” he finally continued, ­“that’s all over now.” He seemed deflated as he moved slowly off the podium, his head bowed. In reverent prayer, ­no doubt.

As we filed out of the gym that day, there were eruptions of song: Because I used to love her, but ­it’s all over now. The Rolling ­Stones’ single. Jagger imitations were followed by adolescent ­laughter.

Speaking of rock and roll. It was five years later, maybe even to the day, in 1969 that the band I was in, newly arrived in San Francisco from Chicago, was playing a series of back-to-school fashion shows in Macy’s department stores all over the California coast. The money was exceptionally good as bookings went (I spent my $350 per week on several pairs of Spanish boots and Lebanese hashish); but whoever was responsible for hiring us was hardly the wisest publicity Twinkie in the ­pack.

We were four very stoned youths, playing at the foot of makeshift plywood runways that supported parades of teenaged models in either minis or longer but slit-up-the-side skirts. The ­Macy’s job was for six weeks, and by the end of the second week, I think, the owner of the studio received a letter from ­Macy’s public relations department. It read something like, “The rock band the Contacts [actually, it was just ‘Contact’] are unreasonably loud as well as poorly groomed. They are disheveled and badly dressed in T-shirts and blue jeans, etc. They are dropping cigarette ashes and butts on the carpets of the various stores where they have appeared, but none of these are our primary complaints. Our concern lies in the complaints from the parents of the models, who report that their daughters are remaining out until all hours with the members of this musical aggregation and returning home under the influence of marijuana and possibly ­LSD.”

As I recall, none of the girls complained, and two of them followed our group around and ended up living with us on Scott Street in San ­Francisco’s Fillmore ­District.

Some three months later, keyboard player Mel Carlson and I attended the Rolling Stones concert at Altamont Speedway in Northern California, where the Age of Aquarius officially ended and the ­Hell’s Angels killed a man in front of the stage. It was all over now, Baby ­Blue.

A year earlier had been the Democratic National Convention and police riot on the streets of Chicago, during which maybe we should have seen the end on the horizon. Six months or so after Altamont would be the Kent State massacre (four students killed, nine wounded by the Ohio National Guard), while the Vietnam War continued taking tens of thousands of lives of members of the same generation. All told, an unnecessarily cruel punctuation to the end of youth and/or life for a hell of a lot of baby ­boomers.

It must be that shift in the light, noticeable in the late afternoon. Streets and homes and businesses, the landscape and ocean, beneath rose and gold ­mare’s tail and bloated cumulus clouds that speak of a breath held a moment before ­autumn.