As was the case with most 60s-rock survivors, the 1980s were not kind to Paul McCartney. Despite ushering in the decade with a pair of blockbusterduets, by 1986s Press to Play, hed hit a commercial and critical nadir, and an artist who once set the pace for rock n roll innovation was stalled in the middle of road. But McCartney eventually wiggled his way out by reminding himself of a lesson that served him well during his Beatles years: He always does his most inspired work with a foil.For 1989s Flowers in the Dirt, he tapped the songwriting smarts of Elvis Costello. Alas, Costello proved not to be Maccas new Lennon—plans for a full-album collaboration were eventually whittled down to a handful of co-writes. (The trove of stripped-down, Elvis-assisted demos featured on Flowers 2017 reissue reveals the album that couldve been.) But the Costello experiment seemed to open McCartney up to more collaborations that would push him outside his usual comfort zone. The most surprising of these was The Fireman, a union with ex-Killing Joke bassist Youth that began in the early 90s as an anonymous ambient-techno project, but reemerged on 2008s Electric Arguments as a cinematically scaled pop group that imagined an alternate 80s where McCartney started taking notes from U2. But The Fireman wasnt even his most outré detour—that honor belongs to Liverpool Sound Collage, a beat-spliced, found-sound curio created with members of Super Furry Animals. And then theres "Cut Me Slack," a 2012 one-off with the surviving members of Nirvana that pushed McCartney toward his "Helter Skelter" heaviest.Alas, these diversions may have been too sporadic to bolster McCartneys long-standing campaign to reclaim the "cool Beatle" status that has long been conferred to John Lennon. After all, in between these side projects, McCartney continued to release solo records of varying quality that captured him in his familiar modes: the piano balladeer, the farmhouse folkie, the Little Richard-schooled rocker. But even his most forgettable albums from the past three decades—like 1993s Off the Ground—feature displays of his melodic mastery (in that case, the golden, slumberous serenade "Winedark Open Sea"). And occasionally, hes let his eccentric streak bleed into his proper albums, like on the epic Driving Rain blowout "Rinse the Raindrops," or the art-pop oddity "Mr. Bellamy" from Memory Almost Full.It says a lot about McCartneys enduring songcraft and capacity for curveballs that his most popular single ever—judging by the nine-digit Spotify streaming numbers, at least—came more than 50 years into his incomparable career. Sure, having both Rihanna and Kanye West sing on it will help boost the stats. And yet, that unlikely but carefree collaboration perfectly crystallizes the latter-day work of an artist whos still pulling from a bottomless well of pretty tunes, but is always four, five seconds from wilding.