Watch the Using Sus Chords online guitar lesson by David Grissom from Open Road Guitar
One of the things that people point out in my style that I didn't really realize that I was doing, is that I use a lot of sus chords in my comping and suspensions when soloing. A sus chord is when we raise the 3rd of a chord up a half step to the 4th. For example A major is spelled AC#E, to make it Asus4 I raise the C# to D giving us ADE. That is the most basic sus we can use. An add9 can also be seen as sus2 chord. So in the key of A Mixolydian I can use some great sus sounds from within the key. We can start with an Aadd9 on the 12th fret, then move it down a whole step to a Gadd9 with A in the bass. That can also be seen as a Dsus4 chord. Now we can go down to a G chord to a basic Asus4 then to a Gadd9. Now I can bring down the root of the Gadd9 chord to F# for a D/A chord then end on a basic A chord. Remember all these as over an open A string. This technique is extremely useful when playing with no other harmonic instruments such as a keyboard player. A lot of this comes out bands I was the only harmonic instrument system is a really great way to fill up some sound. Now let's take a look at the same concept over an Am7 chord. I'm going to play this example without ever actually playing an Am chord. I'm going to play suspensions around that Am7 chord. The chords I am using here are Aadd9, Gadd9, Dmaj, Cmaj, G, Asus, Am11, ending on Aadd9. This is a cool way to add some interesting sounds to a regular minor vamp. Finally, get used to playing some of these ideas in a rhythm context and then you can start to see how you can incorporate them into your soloing.