The art of the cover song is a tricky business. In some cases, the original can simply never be outdone. But in others, a new artist brings whole new notes, layers, textures to a song you never knew were there before. Personally, I have some cover songs that after listening to, I could never possibly go back to the original. (John Mayer's version of "Free Falling," for example...as much as I avoid jumping on the JM bandwagon, you can't deny the man's got soul, plus it's a completely different song than Petty's, and one I can't help but like ten times more.)
The queen of the cover song these last few years has to be Chan Marshall of Cat Power. I'd have to say I advocate checking out all of Marshall's work, (The Greatest, He War, etc) but if you only have time to listen to a few tracks, choose them off her cover album. If you don't already own "Jukebox," Marshall's collections of covers ranging from Dylan to Joplin to Sinatra, BUY THIS NOW. Never have I come across a more essential album of covers, all with Marshall's haunting, breathy vocals carrying each track with a delicate ease. She brings a minimalist, fresh style to each classic, that is undefinable by genre. She has the roughness of a forgotten country singer, the soul and depth of an established blues artist, and the boundless creativity of one of the best and possibly most underrated alternative groups of her decade.
Maybe the true test of an artist is their ability to put their own stamp on a previously created work. If you don't have the depth and range to carry a cover, maybe you never really had all that much to offer to begin with. Afterall, any drunk can karaoke their little heart out to "Free Bird," but it won't do it justice, and it certainly won't make you feel anything. What happens when Marshall puts her stamp on a song is that it becomes irrevocably new and touched by her melancholic, earthy resonance. It is a quirky, religious, undeniably heart-staggering work, drenched in romance. Fill up your tub, pour yourself a cup of tea or maybe a whiskey sour and let Ms. Marshall take care of you for a while.