When Cat Power wrote her steamy open letter to Bob Dylan, "Song for Bobby", for her new covers album Jukebox, she was following a long tradition.
It was a nod not only to Dylan's own "Song to Woody", but to all the words musicians have felt moved to write to each other. Dylan has attracted more than his share, usually bemoaning his latest direction (as with David Bowie's "Song for Bob Dylan" in 1971).
But many others have wanted to get their point across to peers and rivals in the most public way possible. As with Lily Allen's implicitly bitchy "Cheryl Tweedy", or 2Pac and The Notorious B.I.G.'s fatal feud, the sniping can be lacerating – the more so when the rock stars in question know each other uncomfortably well.
CAT POWER to BOB DYLAN
'Song for Bobby' (2008)
This sultry number was inspired by Chan Marshall (aka Cat Power) meeting her hero in Paris last year. She presents herself as a crazed stalker-fan. Marshall's knowingly giddy confession ends with her disbelief at Dylan "supposedly asking to see me", before blurting, "I want you to be my man!"
Watch Cat Power performing 'Song For Bobby' live
BOB DYLAN TO WOODY GUTHRIE
'Song to Woody' (1961)
This was an ambitious 21-year-old's tip of the hat to an elder. He was taking pilgrimages to the Huntington's Disease-stricken radical singer – and adopting his sick, gasping voice – at the time. But he was also using Guthrie as a sounding board to sketch out his future. "The very last thing I'd like to do," he concludes, "is to say I've been hittin' some hard travellin' too". His Never-Ending Tour, and last album set in a Thirties of the mind, start here.
JOHN LENNON to PAUL McCARTNEY
'How Do You Sleep?' (1971)
The bitterly litigious end to The Beatles boiled over in this vicious attack by Lennon on his songwriting ex. "So Sgt Pepper took you by surprise," he begins. Subsequent lyrics align Lennon with the "freaks" and McCartney with "straights", with the latter's career "muzak to my ears". Lennon later claimed the song was written to himself. An even more bilious take chosen by Yoko for the Imagine movie, with the equally disgruntled George Harrison riding shotgun, makes it plain there was only one target.
PAUL McCARTNEY to JOHN LENNON
'Here Today' (1982)
McCartney's initial riposte was Band On the Run's note-perfect Lennon parody "Let Me Roll It", and that album's sheer quality. But Lennon's 1980 murder also inspired McCartney's last great song. Set to brooding "Eleanor Rigby" strings, it is a haiku-elegant, emotionally naked memoir: "I still remember how it was before/and I am holding back the tears no more". An attempt to conjure Lennon by writing to him beyond the grave, it imagines his acerbic response – a final, fantasy collaboration.
PINK FLOYD to SYD BARRETT
'Shine On You Crazy Diamond' (1975)
Pink Floyd seemed to suffer survivors' guilt as they built stadium success on the foundations set by lost leader Syd Barrett, let go as his mind collapsed in 1968. "Shine On You Crazy Diamond" beamed out a cosmic message of support to Syd, wherever he might be: "Remember when you were young, you shone like the sun..." It also implicitly acknowledged the "black hole" he left at their music's core, his loss powering their lucrative melancholy.
LYNYRD SKYNYRD to NEIL YOUNG
'Sweet Home Alabama' (1974)
"Well, I heard Mister Young sing about her/ Well, I heard ol' Neil put her down/ Well, I hope Neil Young will remember/ don't need him around anyhow." Skynyrd songwriter Ronnie Van Zant's response to Young's lurid vision of black people "screamin' and bullwhips cracking" in "Southern Man" (1970), and the similarly hostile "Alabama" (1972), sounded like a declaration of war. That it was the signal in Skynyrd concerts to unfurl the Confederate flag reinforced the impression. In reality, the band were Young fans, and the song mostly attacked his self-righteousness.
JAY-Z to NAS
NAS to JAY-Z
After The Notorious B.I.G.'s murder in 1997, Jay-Z and Nas were the initially friendly rivals for New York's rap crown. "Takeover" turned this into a five-year feud. Over a pumped-up Doors sample, Jay-Z sneers at the veteran Nas's "one hot album every 10-year average", and alludes to having sex with Carmen Bryant, Nas's ex and the mother of his child. Nas hit back twice as hard with "Ether", dismantling Jay-Z's sexuality, even, most cruelly, pitying him ("what's sad is, I love you... you traded your soul for riches"). To be "ethered" became a verb for ruthlessness in hip-hop. Subsequent bouts saw Jay-Z's mum tell him he'd gone too far, and Nas try to hang a Jay-Z effigy. Both rappers, having benefited from the publicity, guested on each other's last albums.
PETE DOHERTY and CARL BARAT to each other
'Can't Stand Me Now' (2004)
The Libertines' final album was made in a spirit of fractious exhaustion between leaders Barat and Doherty, after the latter burgled Barat's flat. "Your light fingers... into darkness cast us," Barat chides. Voices collide, as each puts his case: "Have we enough to keep it together/ Or do we just keep on pretending, and hope our luck is never ending?" Here was the answer. They were finished.
Watch The Libertines' video for 'Can't Stand Me Now
'Jukebox', by Cat Power, is out on Matador