Great Big Sea is the band

 This Americana is from north of the border - NewFOUNDland, to be sure.  "The Night Pat Murphy Died."

Warren Zevon

 

'the bad boy of rock'

Letterman asked Warren Zevon what he's learned from battling cancer.  Zevon replied, "Enjoy every sandwich."

The Wallflowers performed "Lawyers, Guns and Money"  (with Warren's son Jordan ) on Letterman.  This is another cover, by the Killers, at the Rock n Roll HoF....

Washington DC native Nils Lofgren , whose long history includes the E-Street Band

(from 2009)  Nils Lofgren performing the Neal Young song "Long May You Run"...

(and the back story)

"No Kings"

 ...by Jesse Welles

Largest protest in US history and I was there ... so great to be involved ...

"Car Wheels on a Gravel Road"

 This is Lucinda Williams's "Car Wheels on a Gravel Road".

Sad?  Melancholy? Nostalgic?

Yes

"Simple Man"

 

Government Mule, with former Allman Brothers guitarist Warren Haynes, covers the Lynyrd Skynyrd masterpiece, "Simple Man."

songwriting in Nashville

 Tom Snider --- quirky, funny, irreverent.  With something to say about the music business...