When is a reunited rock band not reunited? Black Sabbath are still on tour to promote their most recent album, featuring the same singer, guitarist, and bassist who created the group’s greatest music of 1970 to 1979 – but the drummer Tommy Clufetos is a new recruit, and Rage Against the Machine’s Brad Wilk pounded the skins on the latest disc. The Sabs’ original stickman, Bill Ward, refused to participate in this venture, denied what he called a “signable” contract for his services. So, are Sabbath fans getting the real McCoy, a raw deal, or something else?

The question doesn’t just apply to Black Sabbath. Many of rock ‘n’ roll’s biggest acts now function as fragmentary or 2.0 versions which can discomfit fans and reviewers, if not accountants. The Rolling Stones’ longtime bass player Bill Wyman quit in 1993, and his replacement Daryl Jones is now relegated to auxiliary status (the African-American Jones’ demotion, in a famously blues-based band, seems a little unfair). Upon Who drummer Keith Moon’s death in 1978, he was replaced by Kenney Jones, Jones was later replaced by Zak Starkey, and Pete Townshend and Roger Daltrey have continued to perform as the Who even after the 2002 death of bassist John Entwistle. Kiss had a successful reunion in 1997, but eventually lead guitarist Ace Frehley and drummer Peter Criss were again sacked and their parts and trademark personas have been taken up by other musicians.  Before Glenn Frey’s passing, the Eagles were down to four core members from their 1970s pinnacle, after guitarist Don Felder’s rejection of a deal that left him subordinate to Frey and Don Henley.  AC/DC’s singer Brian Johnson, who took over from the late Bon Scott in 1980, has just recently been sidelined with hearing issues, himself now replaced by Axl Rose of Guns n’ Roses, while co-founder Malcolm Young is incapacitated with dementia and mainstay drummer Phil Rudd is out on legal woes.   Other examples abound.  The Band, the Animals, the Beach Boys, the Doors, Pink Floyd, Sly and the Family Stone – at different times each have recombined in dire and legally contentious approximations of their most famous embodiments.

Like so much else in rock, the myth of group indivisibility began with the Beatles. As early the mid-1960s John, Paul, George and Ringo were already being depicted as cosmically aligned, representing not just ensemble compatibility but a sort of perfect society – the rock critic Greil Marcus said that rock bands were “images of community.” In this greater-than-the-sum-of-the-parts ideal, the absence (or the substitution) of any single member diminished the whole enterprise. Before the Beatles, there was less emphasis on the interpersonal dynamics of pop instrumentalists, even though some configurations were undoubtedly very special: Miles Davis with Charlie Parker, Gene Krupa in Benny Goodman’s swing band, Elvis Presley’s sidemen of Scotty Moore and Bill Black, Motown’s Funk Brothers session aces, and pianist Floyd Cramer’s honky-tonk trills accompanying Patsy Cline. Paul McCartney’s current band has by now probably done more gigs with him than Lennon, Harrison, and Starr ever did, but it’s the cohesion of the Beatles we still venerate; the lineup he currently plays with could consist of anybody.

Yet, as classic rock bands split and only partly reunite, the notion of some magical connection between the original musicians seems less and less tenable. Tribute acts and studio pros have proven that their songs can be accurately duplicated by complete outsiders, and profitable concerts prove that most fans aren’t purists about who exactly is singing or soloing on stage. In his excellent book Like a Rolling Stone: The Strange Life of a Tribute Band, Steven Kurutz noted how some once-famous groups have devolved into “glorified tributes to their former selves…Strictly speaking, is seeing three-sevenths of the classic Lynyrd Skynyrd lineup all that different from seeing a really smoking Lynyrd Skynyrd tribute band?” Middle-aged punters now have to ask themselves what constitutes the authentic manifestation of their favorite teams. Is Michael Anthony more important to Van Halen than David Lee Roth? Would you want to see Deep Purple with Ritchie Blackmore but without Ian Gillan, or vice-versa? Do you value Bill Ward’s contributions to Black Sabbath so much that you’d refuse on principle to see Black Sabbath without him?

Much of this comes down to money. In their heydays, these quartets, quintets, and septets were young men playing for pure love of entertaining, for the music, and for the backstage fun. Years later, though, managers and lawyers have determined the precise earning potential signified by the inclusion or exclusion of each musician in a given band, so who stays in and who stays out is a matter of fine print and balance sheets, more than emotional ties or musical empathy. The legends of 1960s and 1970s rock may not be that different, in the end, from the Las Vegas troupers of yesteryear – duly trotting out their repertoires with any backup of hired guns capable of reproducing them, for any audience willing to accept them as they presently are. The distinction is that Las Vegas troupers were never held, however naively, to any nobler standards of artistic integrity.