The story of these oft-overlooked turtles also points toward an oft-overlooked lineage of apprenticeship in downtown music. In the ’60s, Mr. Young and Ms. Zazeela established an intensive feeding process for their animals: To maintain their health, the turtles would be brought from their aquarium to the kitchen sink to be served shrimp and a complex mixture of brewer’s yeast and calcium. The elaborate task of nourishing Mr. Young’s turtles became a kind of rite of passage for young musicians.
His assistants at the time included the saxophonist and composer Jon Gibson (a founding member of the Philip Glass Ensemble) and the experimental composer Arnold Dreyblatt, both of whom cared for the turtles. Kurt Munkacsi, Glass’s longtime producer and a self-described “herper” — slang for an amphibian and reptile enthusiast — began his career working on Mr. Young’s speaker system, and recalled recently that the turtles “would come out and walk around the loft.”
“His whole lifestyle is like a turtle,” Mr. Munkacsi added of Mr. Young. “He ran on his own clock, and it usually was a very slow clock.” (For a number of years, Mr. Young and Ms. Zazeela lived on an idiosyncratic, self-imposed five-day weekly cycle of 33.6 hours per day.)
In 2005, when the composer Missy Mazzoli needed a summer job during graduate school, she began working for Ms. Monk as a personal assistant and caretaker for Neutron. “I just really bonded with that turtle,” Ms. Mazzoli said. “I didn’t know that turtles had such personalities until I met Neutron.”
For composers who have entered a senior phase in their careers — this concert season commemorates the 80th birthdays of Philip Glass and Steve Reich, two other members of the pathbreaking Minimalist cohort — the lengthy life span of the turtle also raises more sober questions. Ms. Monk, who turns 74 on Nov. 20, said that Neutron “gives you a really different perspective, because of the slowness. It just makes the cycle of your own life — it has a different way of thinking about it.”
“I had to put her in my will,” she added. “She might outlive me.” (Neutron is bequeathed to Ms. Mazzoli, which the younger composer described as “an honor.”)
“Do we have the peace and longevity of turtles?” Mr. Young wondered, speaking in an interview conducted on the evening before his 81st birthday. “Maybe. We developed a way of thinking and hearing and listening that might have been something like how a turtle thinks of sound, or hears sound, or lives in the world of sound.”
The fate of Mr. Young and Ms. Zazeela’s turtles — they have not kept pets in the loft since the late 1960s — is unknown. When the pair began actively touring and invited the Indian musician and guru Pandit Pran Nath to live with them around 1970, they decided it was no longer feasible to care for their menagerie. Mr. Munkacsi carefully packed the turtles in a carry-on bag and flew with them to Georgia, where he released them in a lake near the Okefenokee Swamp.
“Hopefully it turned out well for the turtles,” he said. “Maybe one or two of them got eaten by something. But, probably, most of them did fine: They’re probably still living there.”