Janis Joplin's tough attitude and dynamic vocals have impacted a long list of powerful artists. She's there in the swagger of soul sister Amy Winehouse and the rasp and twang of Lucinda Williams. You can also hear her echoed in more unlikely places, from the wail and stomp of Florence + The Machine's declamatory pop to the heart-on-sleeve lyrics and whip-smart delivery of Liz Phair's gritty alt-rock.