To earn this acievement you need to finish Career Mode on Hard Difficulty.
Uh oh, u gotta stretch for that orange one, (tip, shift and stretch) what do i mean by that? Learn to shift your hand positions around rather than just stretching the pinky.
The career achievements in this game are not stackable wich means you must complete the HARD difficulty to earn the HARD achievement.
The achievement will unlock after you have completed Free Bird by Lynyrd Skynyrd.
Peace and Happy Gaming!