I had a lot of fun playing this so I hope you enjoy as much as I did!
During the solo, the backing chords played are lush and anthemic, something Petrucci attributes to his love of guitarist Alex Lifeson of Rush. One common part of the Dream Theater sound is the add9 chord. The 9th interval is the same as a 2nd interval, but it’s played an octave higher. This interval is common to both major and minor keys, which means you can embellish both major and minor chords, usually without sounding discordant.
You’ll notice a chord with a #11 note (sometimes called a #4th), which is the A# here. This note is found in the E Lydian Mode. The notes are the same as the B Major Scale, but they start on an E to create the Lydian Mode. If you examine the notation you’ll find A# notes dotted throughout the piece – both in the solo and the chord sections – giving a strong overall Lydian flavour.
UPDATE: My friends at Musical U have recently been discussing the Lydian Mode and it’s application here, featuring yours truly. They have some interesting links, one of the highlights being a video featuring the great Rick Beato. You should subscribe to Rick Beato’s channel now if you are serious about music!
As always, below the YouTube video you’ll find the backing track to play along with, and below that, the tablature. Aren’t I nice?!
Feel free to ask questions or just share your thoughts in the comments!