TULL THE FAT LADY SINGS : This ‘Hard Rock’ Band From Britain Will Keep Mining Antiques as Long as Audiences Want

The catch phrase of Jethro Tull’s biggest American hit some 21 years ago was “Let’s go living in the past.”

Ian Anderson, the British band’s leader, evidently meant what he said. The past is Tull’s present agenda, as it brings its tour celebrating the band’s 25th anniversary to Irvine Meadows on Saturday.

There always has been something antiquarian about Tull, even in its early days, when it was forging a distinctive musical style that placed it in rock’s “progressive” sector.

The band, formed in Anderson’s hometown of Blackpool in 1968, looked way back even in naming itself: Jethro Tull was a 17th-Century British agricultural expert who invented a machine for sowing seeds.

Musically, the band gained much of its flavor by turning to British folk roots even older than its namesake, and to the American blues and R&B; that had fueled the first wave of British rock a few years earlier. Anderson began as a guitarist in several lineups that were precursors to Tull, then switched to flute, bringing jazz and classical influences into the mix as well.

On the band’s 1968 debut album, “This Was,” the four members appeared on the cover made up to look like old farmers, but they played music that was an adventurous mix of all the above sources, with the accent on jazz and blues. At the time, guitarist Mick Abrahams had a large say in Tull’s direction; when he left, Anderson was completely in charge.

In an interesting footnote to rock history, Abrahams was briefly replaced by Tony Iommi, who would soon become famous as a lead-and-grunge merchant with Black Sabbath. Could it be that heavy metal would never have been born had Iommi caught on with Tull? Now there’s a pleasant thought. But if so, the Grammy Awards, in one of its trademark faux pas , wouldn’t have been able to award Tull 1988 honors as the best hard rock/heavy metal band. Tull won for an album, “Crest of a Knave,” that had about as much metal content as a starlet’s teeth, giving head-bangers the world over reason to gnash theirs.

In any case, it was Martin Barre who emerged as Tull’s guitarist, and his distinctively sharp, thick-toned riffs and harmonies combined with Anderson’s blasts and swirls on flute to propel the band to rock’s front rank of popularity in the early ‘70s. Barre and Anderson remain the lone holdovers from the early days; the current version of Tull’s oft-changing lineup also includes bassist Dave Pegg, who also is a longtime member of Fairport Convention, drummer Doane Perry, and keyboards player Andy Giddings.

Tull’s golden era hit with a strong series of albums: “Stand Up” (1969), “Benefit” (1970) and “Aqualung” (1971). Turn on your local classic rock station and you’re apt to hear a track from one of them before too long. Anderson’s grousing about organized religion, the main theme of “Aqualung,” now seems tired; but if you can overlook the overfamiliarity of classic rock staples like the title track and “Locomotive Breath,” the album holds up on the vitality of the music and the playing.

“Aqualung” was just the start of Anderson’s predilection for grand concepts. “Thick as a Brick” and “A Passion Play” were album-length pieces that were critically panned for their pretentiousness. As writer Jeff Tamarkin said of “A Passion Play” in a 1988 article in Goldmine: “Anderson’s writing by this time had become so ambiguous that it’s anybody’s guess just what he was saying with the record.” After that, Anderson moved away from writing 40-minute suites, and Tull settled into a steady existence, turning out album after album with slight variations on its well-established sound.

Tull’s latest release, “The Best of Jethro Tull: The Anniversary Collection” (Chrysalis), tacitly acknowledges that the band’s peak came early: The two-CD collection takes 19 tracks to cover the first seven years of the band’s existence and only 17 to encompass the ensuing 17 years. But there are enough high points in the latter-day stuff, especially the more folk-leaning material, to make it a good introduction for the new fan whose ear has been caught by some of those oldies on classic-rock radio and would like to explore further. For the true fanatic, a four-CD boxed set was released last April.

Opening for Tull is the reconstituted Procol Harum, the British band that hit magnificent peaks in the late ‘60s with its stately, classical-influenced organ-piano team of Matthew Fisher and Gary Brooker; Brooker’s passionate, soul-sparked singing, and the edgy blues-rock guitar of Robin Trower. They teamed on such highlights as the single “A Whiter Shade of Pale” and the album “A Salty Dog.” The band’s first run lasted from 1967 to ’77 (only Brooker and the late B.J. Wilson on drums lasted the entire run); Fisher, Brooker, Trower and lyricist Keith Reid regrouped in 1991 for a comeback album, “The Prodigal Stranger,” although Trower has not taken part in Procol Harum’s subsequent touring.