The first Gil Evans repertory concert — or at least, the first one expressly presented that way — took place at Carnegie Hall in 1974, when Evans was still around to steer his orchestra clear of sentimentality. Billed as “an evening devoted to the music and career of Gil Evans,” it was one of the earliest productions of the fledgling New York Jazz Repertory Company, for which Evans was one of several musical directors. He was in his early 60s then, an arranger and composer of pioneering achievement in jazz, and a bandleader not much in the habit of retracing his steps.


That’s worth remembering now, in the face of two big commemorative events. The first, Thursday through Sunday at the Jazz Standard, features the same ensemble heard on “Centennial: Newly Discovered Works of Gil Evans,” an extraordinary album released this week on what would have been Evans’s 100th birthday. The second, next Monday at the Highline Ballroom, will showcase the Gil Evans Orchestra, stocked with alumni and guests and led by the bandleader’s son Miles Evans. Both engagements seem likely to shed new light on Evans as a composer and arranger, which says something about the enduring mystique of his art.


Evans, who died in 1988, has hardly been an obscure figure in jazz. His orchestral work with Miles Davis, especially on the albums “Porgy and Bess” (1958) and “Sketches of Spain” (1960), is widely and justly revered. But the writing he did later, for his own ensembles — and earlier, for the Claude Thornhill Orchestra in the 1940s — still belongs largely to the realm of the connoisseur. In addition to landmark albums like “Out of the Cool” and “The Individualism of Gil Evans,” the Gil Evans legacy encompasses a lot of murky sprawl. It’s impossible to wrap your arms, or your head, around all of it.


At the same time, so much of his vocabulary has been absorbed into the language of jazz orchestration that he can be easy to take for granted. A devotee of classical impressionism, he was obsessive about blends of timbre, often scoring tightly voiced chords for unusual clutches of instruments like French horn and bassoon. He had a way of implying both airiness and compression in his writing, along with a swirling subtlety of movement.


His legacy lives on in the conservatory, naturally, and in occasional tributes like “Sketches of Gil Evans,” presented by Jazz at Lincoln Center in 2007. But it has burned brightest in the expertise of former protégés like the composer Maria Schneider, who had a formative tenure as his copyist and assistant. One of the most impressive feats of jazz repertory I’ve ever heard was at Carnegie Hall in 2000, when Ms. Schneider conducted “Porgy and Bess” and “Sketches of Spain,” bringing a penetrating clarity and three-dimensionality to the music.


A similar astonishment has now come at the hands of Ryan Truesdell, a 32-year-old composer-arranger who is Ms. Schneider’s chief copyist. (He also helped produce her two most recent albums.) Mr. Truesdell spent the last few years tracking down and making sense of previously unrecorded Evans sheet music, with the blessing of the composer’s family. “Centennial,” his first album as a leader, presents a choice sampling of his findings, and makes a strong case for his absolute authority on the subject.


The album — made with crowd-sourced financing through ArtistShare, after an example set by Ms. Schneider — features a superb ensemble with more than a few musicians borrowed from Ms. Schneider’s ranks. The instrumentation often suggests a sort of chamber orchestra rather than a big band; the execution is impeccable, as is the recording quality, with a depth and transparency that capture the endless nuance of the writing.


Half of the album’s 10 tracks date to the Thornhill era, and it’s striking how fresh they sound: even amid the swinging brio of a tune like “How About You,” there are piccolo parts made to lodge a citrusy dissonance. A 1950 arrangement of “The Maids of Cadiz” delivers a more springlike tone than the version heard seven years later, on Miles Davis’s “Miles Ahead.”


Later entries, like a tripartite original titled “Waltz/Variation on the Misery/So Long,” from 1971, and an arrangement of Kurt Weill’s “Barbara Song” revised that same year, feature complex harmonic layering and stark dramatic flourishes. “Punjab,” a castaway from the 1964 sessions for “The Individualism of Gil Evans,” rides a waft of tabla drumming, based on an insight that came to Mr. Truesdell after hearing Evans’s unreleased rehearsal tapes. There’s a brilliant piquancy to all of this music, and Mr. Truesdell succeeds in making his own contribution feel nearly invisible.


Each of his four nights at the Jazz Standard will spotlight a different phase of Evans’s career, beginning on Thursday with the Thornhill era, and continuing on Friday with the reconceived standards from a pair of 1950s albums, including the pertinently titled “New Bottle, Old Wine.” On Saturday the focus will be on “The Individualism of Gil Evans,” and on Sunday it will shift to Evans’s arrangements for singers. (The vocalists will be Kate McGarry and Wendy Gilles, who have one track apiece on “Centennial.”)


If Mr. Truesdell’s labors suggest jazz repertory at its most conscientious — original texts, faithful interpretations — Monday’s concert looks more unwieldy, and more like something Evans might have put together in his later years. Along with veterans like the trombonist Tom Malone and the multi-instrumentalist Howard Johnson, it will feature prominent guests like the drummers Jimmy Cobb and Lenny White, with Paul Shaffer of “Late Show With David Letterman” as host. Anchored by electric bass and keyboards, this band seems predisposed to deal most seriously with the hard-nosed jazz-rock that Evans explored from the ’70s on.


Which would be no truer, or less true, to his memory. During that inaugural season of the New York Jazz Repertory Company, Evans headlined Carnegie Hall yet again, playing a concert of Jimi Hendrix music that was, by most accounts, undercooked. (That didn’t stop him from taking the project into a studio several days later, to record an album for RCA.) The point is that Evans was still pushing, still reaching, defying the notion of jazz repertory as a strictly past-tense concern. “Newly Discovered Works” may be the descriptive subtitle of Mr. Truesdell’s new album, but the phrase also captures what Evans was after all along.