12. Janis Joplin, 'Pearl'
The blues-belting mama’s last stand, released posthumously. Joplin helped invent modern country rock with songs such as the poignant a cappella "Mercedes Benz" and her definitive take on Kris Kristofferson's "Me and Bobby McGee."
Essential moment: Joplin scat-screaming "Hey, hey, hey, Bobby McGee!" as the band cascades behind her.