Warren Zevon did Knockin on Heavin's Door (I believe) after he'd been diagnosed with terminal cancer.
All Along the watchtower cover by Bear McCreary (from Battlestar Galactica)
On YouTube e.g:
Reina Del Cid
Toni ? last name
All 4 very talented and have great covers of everything from Beach Boys (sleep John B) to Stuck in the middle with you, to Ramble on. (Reina and Toni), to Pink Moon (Josh) to Dylan and Beatles and often work together/in various permutations.
Shane Ericks: Superstar or anything by carpenters--sounds very much like Karen