For some reason guitarists tend to avoid music theory which leaves a lot of useful topics unexplored. One of those topics is Extensions.
If you have seen chord names such as Cmaj7, Cmaj9, Cmaj13, Cmaj7(13), and have wondered about the numbers 9, 11, 13, then this lesson is for you! Those numbers refer to Extensions, and they are - as the name implies - a way to extend existing chords/arpeggios to give them some added character. And although extensions are often associated with jazz music, in this lesson I will show you how to use extensions in arpeggios which are suited for melodic passages in any type of music.
In my 7th Arpeggios on 2 Strings lesson I went over a number of useful 7th Arpeggio shapes on two strings. The idea behind that lesson was to show you how 7th arpeggios lend themselves very nicely to execution on two strings and how such two string patterns are very convenient for coming up with smooth, melodic phrasing.
This guitar lesson is a natural extension as I will now show you how easy it is to add arpeggio extensions onto the two string Major 7th arpeggio shapes that you should now be familiar with.
This lesson by definition requires some theory, so read on!
I will talk about chord construction a bit here so if you need some refreshing on how 7th chords are formed, please see the theory section of my 7th Arpeggios on 2 Strings lesson.
First, let's take a look at a C Major Scale:
In the above image, I have circled chord tones in blue and extensions in orange. You probably noticed that the D, being between C and E, could also be called the 2nd. Likewise the F, being between 3rd and 5th, could be called the 4th. So you might be wondering why I didn't label the extensions in the first bar as 2, 4, 6. Typically, by definition extensions are the notes you end up with if you continue stacking thirds after the 7th. So if you go up a third from the B to D (so in this case minor third) we call this note the 9th. Then as you continue stacking more thirds you arrive at the 11 and the 13. But for all intents and purposes 2=9, 4=11, 6=13. Remember this!
The labeling of chord tones and extensions as Root, 3, 5, 7, 9, 11, 13 is based on notes of the Major Scale. When we see things like b5, #9 they are referenced to how a given note is altered compared to the Major Scale. So #9 means "take the 9 from the Major Scale and raise it a half step." This will be important to understand as I go over extensions for other 7th chord types.
When you see a chord labeled as Cmaj9 it means it has same notes as a Cmaj7 but with the added 9th. If you see Cmaj11, it means it has notes of Cmaj7 plus the 9th and the 11th. Similar, Cmaj13 means it has notes of a Cmaj7 but with 9th, 11th, 13th added. If you see Cmaj7(13), where the extension is in parentheses, that means that only the extension in parentheses is added. So a Cmaj7(13) would have C (root), E (3rd), G (5th), B (7th), A (13th).
While piano players can easily play 7th chords with any number of extensions, guitarists tend to use certain principles of substitution which enables us to deal with extensions more easily: A 9th can replace the root. An 11th can replace the 3rd. A 13th can replace the 5th. Remember this!
It is also important to note, that in playing extensions they can be anywhere in the chord or arpeggio, not just after the chord tones. So if you play C D E G B it is a Cmaj9. So is C E G D B. Hopefully you get the idea - ordering doesn't matter. All that matters is the collection of notes.
Ok, with some of these points out of the way, here is a basic guideline for which extensions are typically added to 7th chords: Any note that is not a half step above a chord tone can be added as an extension.
Given that, notice how the F in a C Major Scale is a half step above the E? If we were to add F to a Cmaj7 chord to form a Cmaj7(11), it would sound rather dissonant with the 3rd there in the chord along with that F up a half step. That doesn't mean dissonance is bad. These are just some basic guidelines. Good to know about them before discarding them!
So with a Major 7th chord, while you won't often see a Maj11 or Maj7(11), you can raise the F to an F# from which you can form a Maj7(#11), for instance.
So for a Maj7 chord, the most common extensions are 9, #11, and 13. #9 is also fine since it is not a half step above a chord tone (the relevant chord tone in this case being the root). Other chord types are less strict about which extensions are added, such as Dominant 7 chords. We'll get to those later. For now let's see how top use this knowledge to form some cool sounding arpeggio patterns!