He’ll always be The Boss, but Bruce Springsteen has also been the assistant more times than you might realize, guest appearing on dozens of songs by an eclectic list of, no doubt, very grateful artists over the years.

Several, as what might be considered Springsteen’s “extended musical family,” are to be expected: Nils Lofgren (‘Valentine’), Southside Johnny (‘It’s Been A Long Time’), Jesse Malin (‘Broken Radio’), and Gary U.S. Bonds (‘This Little Girl’ and ‘Jole Blon’). More surprisingly, perhaps, were partnerships with Joe Ely (‘All Just To Get To You’), Graham Parker (‘Endless Night’), Alejandro Escovedo (‘Faith’), Rosanne Cash (‘Sea Of Heartbreak’), and an Everly Brothers cover with John Fogerty (‘When Will I Be Loved’). Bruce even collaborated once with Celtic punk band Dropkick Murphy’s on ‘Rose Tattoo’ and with disco diva Donna Summer on ‘Protection’ – which Springsteen wrote for Summer, who recorded it in 1982, but whose duet vocal version with Bruce remains unreleased and elusive. Sidekick supremacy, however, at least to me, must go to Springsteen’s powerful and yet even more poignant role supporting Warren Zevon on his 2003 fireball ‘Disorder In The House,’ a song Zevon recorded with more than just a record company release schedule hanging over his head.

After more than three decades of slyly sardonic pop masterworks, and at the age of just 55, Zevon was diagnosed with terminal cancer following a brief period of experiencing shortness of breath (he later noted “I may have made a tactical error in not going to a physician for 20 years”). Refusing treatments he believed would incapacitate him, he instead began work on what everyone involved knew would be his final album. It was entitled “The Wind,” included the gut-wrenching farewell tune ‘Keep Me In Your Heart,’ and it ultimately received two posthumous Grammys – the only two of Zevon’s career – one for the album, and the other for the aforementioned duet with Warren’s friend Bruce. Watching the two of them together in the attached video – part of the VH-1 documentary film, “Inside Out: Warren Zevon” – is at once an experience of jubilance and melancholy. Zevon appears frail, even, at times, shaky, but he literally becomes enlivened by the superhuman powers of Springsteen, who, between vocal exchanges, positively wails not one, not two, but three consecutive scalding guitar solos directly into Zevon’s awaiting lap, a furious pre-death elegy delivered by Bruce’s mighty Fender Telecaster.

In October of 2002, not long after his diagnosis nor before his demise, Zevon was featured on the Late Show with David Letterman as the only guest for the entire hour. It was during this broadcast that, when asked by Letterman if he now knew something more about life and death, the indomitable Zevon first offered his oft-quoted quip of insight: “Enjoy every sandwich.” Watching Zevon witnessing his short-lived sideman Springsteen’s frenetic performance in ‘Disorder In The House,’ I wouldn’t be surprised if this was the moment Zevon came to that elementary epiphany. He certainly seems to be unmistakably enjoying the contributions of his able assistant, The Boss, who certainly played like it was a matter of life and death.

Warren’s last stand with Dave