This is an odd time (7/4) riff that is all sixteenth notes. Guitarist John Petrucci plays this song on a 7 string guitar. The opening riff of the song requires the 7th string, thus in my tab I cover the part of the riff that can be played on a six string guitar.
The riff begins at 0:33 in the song.
The first three sixteenth note groupings are straightforward with the accent note falling on the first beat. The next two sixteenth note groupings are a bit trickier, as the accent note falls on the 3rd sixteenth note in each group. The sixth sixteenth note grouping is played on the open string, and the seventh grouping is similar to the first three.
The challenge of this riff is synchronizing the left with the right hand. While the right hand maintains a steady sixteenth note picking rhythm, the left hand must navigate on beat and offbeat accents.
It’s a fun riff to play that sounds great and will help you develop your alternate picking skills!