NEW YORK (NYTIMES) - Saxophonist Sonny Rollins, perhaps jazz's most respected living improviser, is also one of its most relentless seekers. But that's well known; what's not as widely recognised is the diversity - and the depth - of his inquiry.

Yes, there's his herculean practice regimen (upward of eight hours a day, even into middle age) and the yearslong sabbaticals he took from performing to hone his craft. But Rollins, 86, has also maintained a vigorous, syncretic spiritual practice, and he has written hundreds of pages of personal notes over the years - reflecting on music technique and the music business and expressing social laments. He even started writing an instructional saxophone book but dropped that project.

These are among the insights to be gleaned from Rollins' personal archive, which the Schomburg Center for Research in Black Culture, part of the New York Public Library, has acquired. The centre will process the archive and eventually make it accessible to the public.

"I felt that if any young musicians or people were interested in my life and my career, this should be available," Rollins said in a recent telephone interview. "I'm an introspective person," he added. "I always liked to improve myself, and I always liked to learn." The archive includes hundreds of recordings from Rollins' rehearsals and practice sessions, largely from the 1970s and 1980s; hundreds of pages of musical notation; a Selmer saxophone that he remembers playing as far back as the 1950s; scores of letters to and from his wife, Lucille, who managed his career starting in the 1970s; and a steady stream of philosophical, often self-scrutinising notes.

Rollins trusted his materials to the Schomburg Center partly because of a personal connection: He was born just two blocks away, and grew up in Harlem and Washington Heights. (He remembers going to the centre as a child to check out a book for school.) The announcement about Rollins' collection comes on the heels of another major purchase of materials from a Harlem native: The centre announced in April that it had acquired the personal archive of writer James Baldwin.

"That's one of our big desires: to bring the sons and daughters of Harlem home," said Kevin Young, director of the Schomburg Center. "The context here is really rich. It's not just coming home in the sense of a physical place. It's also coming home to the body of reference and inference and connection that we've been building up for 92 years." The library declined to disclose the purchase price.

The archive also contributes to a small resurgence in the conversation around Rollins, who has not performed publicly for the past four years because of ailing health. A campaign recently began to have the Williamsburg Bridge, where he practised in isolation almost daily from 1959-1961, renamed for him. And on June 9, at Flushing Town Hall, his longtime confidant Jimmy Heath will lead the Queens Jazz Orchestra in a tribute concert.

It could take years to digitise and catalogue the Rollins archive, which includes some notes from the bridge period; then the archive will be spread across four of the centre's five divisions and made searchable online. The centre does not have plans for major exhibitions of the material, but Rollins' home and studio recordings will become part of the Moving Image and Recorded Sound Division, which is to be renovated soon.

When Rollins hit the national jazz scene in the early 1950s, he seemed to possess a new kind of energy. Unlike Coleman Hawkins or Lester Young, whose mantle he picked up, Rollins rarely purred into his horn. He sounded as if he were trying to push himself fully into every note, intentionally and bodily and without guile - as if it were the only way he would have any shot at getting his point across.

Rollins seldom performed with a large ensemble, preferring to maximise his direct contact with the listener. He introduced the saxophone-bass-drums trio before almost anyone else, and, in concert, his solos could often run well over 10 minutes.

But if Rollins has always worked to put himself in plain view, he was incessantly aware of what he saw as his shortcomings. Throughout his papers, he seems constantly to be driven by complementary impulses: the feeling that his tools - however prodigious - are not quite sufficient to the task, and a hunger to specify the paths of improvement.

To achieve as much power as possible, Rollins recognised early that he would need to give up cigarettes, and he began to meditate and practice yoga well before they were common practices in the West. (He was addicted to heroin from the late 1940s to the mid-50s but entered a rehabilitation clinic and recovered.) The archives show that he even started the Sonny Rollins Yoga for Americans Club (or at least printed and used stationery for it). He established correspondences with spiritual gurus and yoga teachers abroad, all of which are reflected in the archive, along with photos taken during a trip to Japan.

In this way, the collection will inform what is already apparent in Rollins' sound: He is a physical player, whose improvisations and compositions - from St. Thomas to The Freedom Suite - convey a sense of well-plotted, multidirectional movement. Throughout his career, his solos have been full of rhythmic variations that tug his melodies in unexpected directions.

This isn't by accident. The archive includes personal notes on breathing exercises and a full-page sketch of the bones making up the human core. (Rollins, who had briefly considered a career as a cartoonist, has always sketched constantly.) On one notebook page, he maps out a concept for how his band might file onstage, having already begun its first tune, as a way to make literal the music's implications of movement - and involve the audience.

It's clear Rollins has an affinity for the written word. Throughout his archive, he penned ruminations on musical best practices, race relations and the frustrations of the jazz industry. These writings are not collected in any organised journal, but they are identifiable by Rollins' formal and declarative linguistic style.

He often found himself frustrated with what he saw as the superficial (and culturally oblivious) treatment of his music by most jazz journalists - but he never stopped paying attention to them. He saved dozens of magazine clippings about himself.

When Rollins released The Freedom Suite in 1958, the first major work by a jazz musician to address civil rights concerns, he accompanied it with eloquent and persuasive liner notes. "How ironic that the Negro, who more than any other people can claim America's culture as his own, is being persecuted and repressed, that the Negro, who has exemplified the humanities in his very existence, is being rewarded with inhumanity," he wrote. The Schomburg's collection includes personal notations that he wrote while working on the text for the album.

Why did Rollins never turn his thoughts and his expansive personal history into a book? The explanation is quintessential Rollins.

"I felt that I needed more to learn," he said. "I always felt that I wanted to live more life. I wanted to find out a little more before I wrote about it."