Plenty of acts deserve box sets, and even more are capable of filling them, but few actually require them in order to capture a sense of their scope. Indisputably, one such act is The Isley Brothers, done right by It's Your Thing, a new three-disc collection. The long, complicated, and illustrative recorded history of The Isley Brothers effectively begins with the much-covered 1959 oldies-radio staple "Shout" and twists and turns (and occasionally shouts) its way through decades of R&B history. Formed in Cincinnati, the original lineup of Rudolph, Ronald, and O'Kelly Isley began, like many soul groups, singing gospel music, only switching to secular material after the death of a brother broke up the quartet. After a string of indirect hits—far more people heard The Beatles' version of "Twist And Shout" than the Isleys'—the group formed its own label, T-Neck, seized an unusual amount of control for black artists in the '60s, and hired, for a little while, a little-known guitarist named Jimi Hendrix. As illustrated by two scorching, Hendrix-backed proto-funk tracks—which always seem to be on the verge of losing control, but never do—the group knew quite well how to be ahead of its time. But it also knew how to be precisely in the moment: A short-lived stay at Motown found the group doing well by the Holland/Dozier/Holland songbook, but as good as "This Old Heart Of Mine" sounds coming from The Isley Brothers, it would work just as well coming from any number of Motown artists. The late '60s and early '70s found the group sounding just far enough ahead of its time to be totally right for it. Before "It's Your Thing" became an anthem for fast-food patrons across the land, it and the Isleys helped take R&B in a funkier direction during the pre-disco glory days of politically charged, unapologetically forward-sounding music. Shaking things up at this point was a younger generation of Isleys, thanks to the addition of two more brothers (Marvin and Ernie) and a brother-in-law (Chris Jasper). Ernie Isley in particular deserves credit for his stunning guitar work, which brings back some of the rock power of Hendrix without sounding imitative, but the collective sound of the six-man Isley Brothers lineup is the sound of one of the most impressive R&B units ever assembled, working in top form. "Thing," "That Lady," "Fight The Power," and others burn with a rare intensity, while a Marvin Gaye influence adds a tender side. Also interesting from this era is the group's tendency to rework songs by white artists, sometimes to the point of unrecognizability; James Taylor's "Fire And Rain" and Seals And Crofts' "Summer Breeze" sound decidedly different in the group's hands. (There's even a pointedly titled 1971 album of covers called Givin' It Back, featuring the Isleys toting singer-songwriterly acoustic guitars on its cover.) Unfortunately, the brothers eventually took the mellowing process too far and, aside from cuts pulled from the Gaye-influenced 1976 album Harvest For The World, It's Your Thing's third disc doesn't command much attention. The unkind '80s saw The Isley Brothers chasing trends instead of leading them, turning out too many paint-by-numbers slow jams, suffering from internal discord, and mourning the death of O'Kelly Isley in 1986. But for more than two decades, the Isleys had their thing down cold, and for more than two discs, so does this well-assembled and lovingly annotated collection.