Here’s a fun idea that I love using. Let’s solo over a sequence that has very limited harmonic structure. We’ll find a track that has just one power chord. You can have another guitar player play this for you if you want, or even a bassist. Let’s say they are playing an E5. Now, which scale or scales can you play over that chord. Well, over an E5 you can play many scales and modes. Start comfortably, soloing with your usual licks, then switch into a parallel scale. For example, E Dorian to E Lydian or E Mixolydian to E Phrygian. All of these combo’s work! Joe Satriani refers to this as a “pitch axis” saying that each scale has a relationship to the central pitch. I also use the term parallel, which means, “sharing the same root note”.
There are two ways you can approach this concept – melodically or harmonically. The first way, melodically, is how I described it. You will solo over a track with minimal harmonic structure – no full triads, one static power chord only for now (temporary rules, remember?). Freely change modes or scales and see what you can come up with. Listen to Steve Vai’s “The Riddle” on Passion and Warfare for an example. The second approach, harmonically, is to use a pedal tone (or pitch axis) for chords. Let’s use E, and play chords with an E root note that impose certain modes. For example over an E pedal tone, play Em7 to E7#11. That would imply E Dorian (but not just), to E Lydian b7. Satriani’s “Lords of Karma” from Surfing With the Alien or “With Jupiter In Mind” from Crystal Planet will serve as great examples here. Use a jam track, record a track of your own or toss this idea around at your next band rehearsal or jam. Have at it! Enjoy!