What’s the difference between add9, Maj9 and 9 chords?

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Written for Guitar-Muse.com:

As a guitar teacher I see a lot of confusion, even among my more advanced students, when it comes to playing these types of chords. Truly knowing how to voice these chords comes from an understanding about how chord naming conventions tie into music theory. Let’s explore the subject by taking a look at the difference between add9, Maj9 and 9 chords. [READ MORE]