When you know music theory, you can utilize that knowledge to create some really cool sounds with your instrument.
Joe Satriani is a man who REALLY knows music theory.
Joe gives a lesson with Guitar World where he demonstrates stacking fourths (intervals) to create some pretty awesome sounding chords in E Dorian.
Check it out:
Thankfully, Guitar World has been kind enough to provide tabs for the examples in this lesson. CLICK HERE to see what Joe played!
2nd intervals are pretty damn cool. They are most commonly heard in suspended 2nd chords. Well, that's at least where I typically seem to hear and see them being used.
Used correctly, 2nd intervals can add a very unique sound to what you're playing/writing.
What is a 2nd interval? A 2nd interval is one whole step up from a root note. For example: the 2nd interval of G is A. A is one whole step above G (in other words, 2 frets higher).
You can also have a flat 2nd interval, aka: minor 2nd. A flat 2nd interval is a half step above the root note. For example, the flat 2nd interval of B is C. C is one half step above B (in other words, 1 fret higher).
Joel Hoekstra put together some really cool sounding exercises to help you get familiar with the sounds of 2nds. Here's the video lesson he did with Guitar World:
Tabs for this lesson can be found here: www.guitarworld.com/lessons-artist-lessons-rock/applying-second-intervals-arpeggiated-riff-ideas/29966
John Taylor - guitar and bass instructor for Mile High Shred.