Watch the To The 9's online guitar lesson by Corey Congilio from 50 Blues Rhythms You MUST Know
Up to this point we've played blues rhythms using 7th and root/5 power chords. The 7th chords we've used create a solid foundation for blues rhythms. These chords also leave that dominant bluesy stamp on our mind's ear! 9th chords are very popular in blues rhythm playing. The 9th sound is often considered jazzy or funky.
I believe people associate these words with 9th chords because we're incorporating notes that are getting further away from the familiar root, 3rd, 5th chord tones. Like always, use these chords if they sound good. Don't try to force them where they don't belong. Let the tune dictate their use.
Also, at the heart of every 9th chords is a 7th chord. If a song calls for a 9th and you play a 7th, no worries. You'll get it the next time around. After all, most blues is 12 repeating bars of dominant chordal goodness!
This example is a slow blues. Typically slow blues songs are in a 12/8 time signature and full of 9th chord sounds. This is a basic version so, enjoy!