Lenny Kravitz's rollicking guitar swagger created a blueprint for numerous retro rock ‘n' rollers. You can hear his funk-based riffage in Ben Harper's smooth “Black Rain” and his amplified, head-nodding rhythms in the wah pedal of Kid Rock's “Roving Gangster (Rollin').” And D'Angelo's slinky “The Root,” with its smoky delivery and jazzy six-string lines, recalls Kravitz's neo-soul leanings.