Duane Allman appeared on the scene with an aggressive slide style that seemed to incorporate as many blues harp licks as it did Delta or Chicago guitar.
The classic "Live at The Fillmore" album has standout tracks like "Statesboro Blues" and "One Way Out" that influenced future slide players for generations.
Here's TAB and a Practice Track of the "Statesboro Blues" progression to practice your Duane-inspired licks.
Practice Track: