50 years of Jethro Tull. “How did that happen?” founding singer, songwriter, harmonica player, and flautist extraordinaire Ian Anderson rhetorically asked the Greek’s capacity crowd. Certainly, it happened on the strength of the progressive rock champions’ iconic stable of FM classics, unique instrumentation, and elevated sense of musicianship, represented here by Anderson’s solo band, in as much a comprehensive celebration of five decades of Tull as possible.

Sure, an inclusion of longtime guitarist Martin Barre—a former member who’s still actively touring the catalog—would’ve thrilled the die-hards, and, really, an appearance by any of the 36 other musicians that have spent time in the band since 1968 could’ve been special, but that misses the point: This was not a Jethro Tull reunion. This was Ian Anderson honoring the group’s 50th anniversary. It’s not a semantic distinction, though Anderson and Tull have been for years confused or conflated as one and the same. This is Anderson and his solo touring unit dedicating two sets solely to the music he created and performed with Jethro Tull.

And, it wasn’t just the music. The entire experience, from pre-show videos tracing the band’s chronology and Tull shirts and paraphernalia dominating the merch stand to taped interludes between songs featuring recollections, well-wishes, and introductions running the gamut of members and admirers- from Clive Bunker and Joe Bonamassa to Tony Iomi and Slash- was a grand thank-you to the influential group.

Chief among those and their gratitude is Anderson, himself, who with typical grace and humor prefaced each song with an informing tale or tribute. It cannot be ignored that his instantly recognizable voice has been re-invented as a breathy, behind-the-beat interpretation; one that is less cutting and powerful than of his youth, but affecting still in its honesty. Granted, there was the rapidity of verses in the penultimate “Aqualung” that necessitated some assistance from the video board, but mostly it was Anderson tackling even the trickiest vocal turns with determination.

As for the flute, perhaps as much if not more identified with Anderson as his voice, it floated and darted as wistfully and sharply as ever. His trademark playing stance, up on one leg, came early, on the third entry, “A Song for Jeffrey,” after an opening duo of “My Sunday Feeling” and “Love Story.” The jazz, blues, and classical signposts of the budding repertoire were all there on “Dharma for One” and “A New Day Yesterday,” then transitioned to the hybridized style that became their signature on a set-closing “Cross-Eyed Mary.”

The second half rippled through the title tracks of their ‘70s album zenith: “Thick as a Brick,” “A Passion Play,” “Songs From the Wood,” “Heavy Horses,” and, of course, the irony of “Too Old to Rock ‘n’ Roll, Too Young to Die.” Only “Farm on the Freeway” documented the latter course of the band, when they became an unintended punchline after winning a Heavy Metal Grammy; mostly every song was a favorite of the heyday, with even more left on the cupboard shelf. After the crescendo of the “Locomotive Breath” encore rang out, Anderson and his first-rate band took a final bow, accepting the lasting applause for this evening of celebrating Jethro Tull and all that came before. To answer Anderson’s question, performing these indelible songs with dignity and flair is how 50 years happens.