Throughout the 1970s prime of progressive rock, numerous bands took a “symphonic” approach, piling instruments into ornate soundscapes. But Jethro Tull earned that label more literally: Aided by orchestral arranger Dee Palmer, mastermind Ian Anderson composed masterpiece LPs like 1971’s Aqualung and the following year’s Thick as a Brick with space for legitimate string sections. On 1975’s Minstrel in the Gallery, the orchestra is beyond decorative—as essential to the songs as the bandleader’s zig-zagging flute or Martin Barre’s thunderous electric guitar. So on first glance, the concept for Anderson’s latest Tull outing feels redundant. Why bother with String Quartets when you could savor the thrill of rock meeting full-blown orchestra? But the album proves more daring—and engrossing—than the title suggests. Collaborating with arranger John O’Hara and the Carducci Quartet, Anderson discovers new harmonic depth in straightforward compositions like “Bungle in the Jungle” and “Living in the Past.” (Eternal riff-monster “Locomotive Breath” is revamped with an opening, Bach-inspired cello cadenza.) And by reworking already complex material, like a breathtaking hybrid of “Songs From the Wood” and “Heavy Horses,” the musicians highlight the elegance of the original themes, embellishing only with minimal flourishes. Even in this “guest” setting, adding brief vocal and flute parts on select tracks, the ever-magnetic Anderson emerges as the star: With his trademark “over-blowing” flute technique in full force, “Farm on the Freeway” is transformed from a middle-of-the-road ‘80s ballad into a bone-rattling epic.