 The four difficulty levels for each song afford the player a learning curve in order to help him / her progress in skill . The first difficulty level , Easy , only focuses on the first three fret buttons while displaying a significantly reduced amount of notes for the player to play . <unk> introduces the fourth ( blue ) fret button , and Hard includes the final fret button while adding additional notes . The addition of the orange fret button forces players to move their fingers up and down the neck . Expert does not introduce any other frets to learn , but adds more notes in a manner designed to challenge the player and to simulate the player 's hands to move in a sequence similar to a real guitar . A difficulty added in World Tour is <unk> , which only requires the player to strum to the basic rhythm ; holding the fret buttons becomes unnecessary . Another new difficulty only for drums was added to Metallica known as Expert + , which uses the double bass pedal . 
