Hey all! Rodrigo here again!
Greetings and welcome back to the sixth lesson in our series on guitar theory! In today’s article we’ll learn about Shell chord voicings, which are the most practical chords, as well as chord’s extensions (9ths, 11ths, 13ths, and many others). Therefore, before continuing, make sure you have a firm grasp of 7th chords and compound intervals. If you're new around here, I've been posting all of these articles in the "right" order to make it easier for you to understand how music theory applies to the guitar.
Simples Intervals -> Compound Intervals -> Triads -> Drop-2 Chords -> Drop-3 Chords -> Shell Chords & Extensions -> Triads & Extensions -> Arranging with Drop-2 Chords -> Guitar Arpeggios
And if you think this material has been helpful to you, please leave a comment at the bottom of the page. Have fun!
WHAT ARE SHELL CHORDS?
Shell chord voicings are three-note voicings for seventh chords consisting of the root, 3rd and 7th of each chord. By omitting the 5th, we can create generic voicings that are suitable for many different situations, not to mention that these chords require very simple fingerings and are very popular among blues and jazz guitarists.
Let’s take the Cmaj7 chord as an example! Cmaj7 is made up of the following notes C (root), E (major 3rd), G (perfect 5th), and B (major 7th). In contrast to the Drop-2 and Drop-3 voicings that we have worked on in the previous articles, when the fifth is left out, there are five different and simpler ways to play it on the guitar fretboard:
MAJOR 7th “Shell chord voicings”
[Cmaj7 “Shell voicing” on the higher strings]
C E B [R 3 7]
[Cmaj7 “Shell voicing” on the mid-higher strings]
C E B [R 3 7]
[Cmaj7 “Shell voicing” on the mid-lower strings]
C E B [R 3 7]
[Cmaj7 “Shell voicing” on the lower strings]
C E B [R 3 7]
[Cmaj7 “Shell voicing” on the lower strings skipping the A string]
C B E [R 7 3]
Before I explain why these chords are so important, I wanted to show you some additional shell chord voicings. I'd like you to play them all right now on your guitar! Note how simple their shapes are in comparison to the other chords we've learned and any other chords you knew before this lesson:
MINOR 7th “Shell chord voicings”
[Cmin7 “Shell voicing” on the higher strings]
C Eb Bb [R b3 b7]
[Cmin7 “Shell voicing” on the mid-higher strings]
C Eb Bb [R b3 b7]
[Cmin7 “Shell voicing” on the mid-lower strings]
C Eb Bb [R b3 b7]
[Cmin7 “Shell voicing” on the lower strings]
C Eb Bb [R b3 b7]
[Cmin7 “Shell voicing” on the lower strings skipping the A string]
C Bb Eb [R b7 b3]
DOMINANT 7th “Shell chord voicings”
[C7 “Shell voicing” on the higher strings]
C E Bb [R 3 b7]
[C7 “Shell voicing” on the mid-higher strings]
C E Bb [R 3 b7]
[C7 “Shell voicing” on the mid-lower strings]
C E Bb [R 3 b7]
[C7 “Shell voicing” on the lower strings]
C E Bb [R 3 b7]
[C7 “Shell voicing” on the lower strings skipping the A string]
C Bb E [R b7 3]
DIMINISHED 7th “Shell chord voicings”
[Cdim7 “Shell voicing” on the higher strings]
C Eb Bbb [R b3 bb7]
[Cdim7 “Shell voicing” on the mid-higher strings]
C Eb Bbb [R b3 bb7]
[Cdim7 “Shell voicing” on the mid-lower strings]
C Eb Bbb [R b3 bb7]
[Cdim7 “Shell voicing” on the lower strings]
C Eb Bbb [R b3 bb7]
[Cdim7 “Shell voicing” on the lower strings skipping the A string]
C Bbb Eb [R bb7 b3]
WHY ARE SHELL CHORDS SO IMPORTANT?
I'll answer this question in two parts. Remember what I said about how shell chords are useful in a variety of situations? When the 5th is omitted, the quality of this interval has no effect on how we describe chords anymore. For example, the Cmaj7 shell chord voicing is identical to the Cmaj7(#5) and Cmaj7(b5); the Cmin7 shell chord voicing is identical to the Cmin7(b5); the C7 shell chord voicing is identical to the C7(#5) and C7(b5); and the Cdim7 shell chord voicing is identical to the Cm6.
Several musicians like to play the triad in conjunction with their shell chord voicing, so that it not only provides the entire chord color, but also creates a more interesting voice movement on the top note:
[Dmin7(b5) “Shell voicing” in conjunction with the Ddim triad]
The following example depicts a well-known chord progression known as "II V I," which we will go over in depth in the future, but for now we're just using it to demonstrate the previous Cmin7(b5) applied to a context.
[Dmin7(b5) “Shell voicing” in conjunction with the Ddim triad in a II V I progression]
The second reason you should learn shell chords is that we can easily add an extra note to them. The reason is simple: when thinking of Drop-2 chords, for example, we usually use all four fingers to play the entire voicing. On the other hand, because we always have one free finger when playing shell chords, it is much easier to use it to add any extra note/color to chords. Keep this in mind, because we'll find out what these extra notes are in the following paragraphs.
One more thing before we go! The "correct" notation of a shell chord voicing must include a "(omit. 5)" or "(no 5)" right after the chord symbol, such as: Cmaj7(omit.5) or Cmaj7(no 5). Not many people use this type of notation anymore, but if you see something like that in the future, you already know what it means. For the purposes of this article, consider that all of the following chords will be shown in shell chord voicing format.
TENSION vs. CHORD TONE (Upper structure vs. Lower structure)
Chord tones, as defined in the Triads article, are the notes used in the formation of any chord. Using Cmaj7 as an example, this chord is made up of four notes: C (root), E (major 3rd), G (perfect 5th), and B (major seventh), and these four notes are the chord tones. Any remaining notes (Db, D, D#, F, F#, Ab, A, Bb) will be referred to as tensions.
These eight remaining notes are respectively the Db (minor 2nd), D (major 2nd), D# (augmented 2nd), F (perfect 4th), F# (augmented 4th), Ab (minor 6th), A (major sixth), and Bb (minor 7th), and whenever we refer to a note as a tension, we will use its compound interval to name it. Then, if we add the D, for example, to the Cmaj7 chord, we'll call it Cmaj7(add9).
[Cmaj7(add9) “Shell voicing” on the mid strings]
C E B D [R 3 7 9]
If we add the F# to the Cmaj7 chord, we'll call it Cmaj7(add#11).
[Cmaj7(add#11) “Shell voicing” on the lower strings skipping the A string]
C B E F# [R 7 3 #11]
If we add the A to the Cmaj7 chord, we will call it Cmaj7(add13).
[Cmaj7(add13) “Shell voicing” on the lower strings skipping the A string]
C B E A [R 7 3 13]
When naming chord tones, we will always use their respective simple intervals, i.e., thirds, fifths, sevenths, and so on; and when naming tensions, we will always use their respective compound intervals, i.e., ninths, elevenths, sixteenths, and so forth. As a result, chord tones are always referred to as the "lower structure" of the chord, while tensions are referred to as the "upper structure" of the chord.
Before we continue, it is important to note that when writing the chord symbol, many people will add the tensions between parentheses without using the term "add," i.e., Cmaj7 (9). That's fine; this isn't incorrect! However, I chose to always use the abbreviation "add" before the tension, so that when we see chords like Cmin7(b5)add11, we know that the 11th is a tension and the b5 is a chord tone!
AVAILABLE TENSION vs. AVOIDED NOTE
In the previous topic, we learned the difference between tension and chord tone, but not all of the eight remaining notes would complement Cmaj7. In music, we refer to certain notes as "avoided notes" because they can create a dissonant sound when combined with a chord, which can negatively affect its overall quality. To identify avoided notes, it is important to remember two rules. Firstly, any note a half-step above any chord tone must be avoided. For instance, the Db note should not be played in Cmaj7 as it is a half-step above C. Similarly, F should also be avoided as it is a half-step above E, and Ab because it is a half-step above G. Secondly, no chord can have both the major and minor sevenths. Therefore, for Cmaj7, the Bb (minor seventh) must also be avoided.
We are left with only four notes: D, D#, F#, and A. These notes are all available tensions that we can add to the Cmaj7 chord. If we add the D (which is the 2nd of C), we call it Cmaj7(add9) or Cmaj7(9). If we add the F# (which is the augmented 4th of C), we call it Cmaj7(add#11) or Cmaj7(11). Adding the A (the major sixth of C) makes it Cmaj7(add13) or Cmaj7(13). We use the compound interval to name the tensions.
While many people believe that the only available tensions for a maj7 chord are the 9th, the #11th, and the 13th, adding D# (the augmented 9th) makes Cmaj7(add#9). This chord comes from the sixth degree of the harmonic minor scale and generates the Lydian #2 mode.
Before we move on, I'd like to add one more item to the list, which is not exactly a rule but rather an exception to the previous two. The function of dominant chords is to add tension and resolve to other chords, both major and minor. Dominant chords, such as C7, C7(#5), C7(b5), and C7sus4, can handle most of the tensions. These tensions include b9th, 9th, #9th, #11th, b13th, 13th, b17th, and 17th. In the next part of this article, I will discuss each of these exceptions more comprehensively as we go through all the 13 types of 7th chords and their extensions. Remember, the only unalterable rule is the one regarding 7ths.
TABLE OF TENSIONS
Below are images displaying the most frequently used shell chord voicings with different tensions, as listed in the table above. It's worth noting that numerous other possible combinations exist, and it's up to you to experiment and exercise creativity. Remember to explore beyond the given examples!
MAJOR 7th “Shell chord voicings”
Cmaj7 on the mid-lower strings [R 3 7]
Cmaj7 on the middle strings w/ add9 [R 3 7 9]
Cmaj7 on the middle strings w/ add#9 [R 3 7 #9]
Cmaj7 on the lower strings w/ add#11 [R 7 3 #11]
Cmaj7 on the lower strings w/ add13 [R 7 3 13]
The Ionian mode (first degree of the major scale) generates the tensions 9th and 13th.
The Lydian mode (fourth degree of the major scale) generates the tensions 9th, #11th, and 13th.
*The Lydian #2 mode (sixth degree of the harmonic minor scale) generates the tensions #9th, #11th, and 13th.
MINOR 7th “Shell chord voicings”
Cmin7 on the mid-lower strings [R b3 b7]
Cmin7 on the middle strings w/ add9 [R b3 b7 9]
Cmin7 on the lower strings w/ add11 [R b7 b3 11]
Cmin7 on the lower strings w/ add#11 [R b7 b3 #11]
Cmin7 on the lower strings w/ add13 [R b7 b3 13]
The Aeolian mode (sixth degree of the major scale) generates the tensions 9th and 11th.
The Phrygian mode (third degree of the major scale) generates the tension 11th.
The Dorian mode (second degree of the major scale) generates the tensions 9th, 11th, and 13th.
**The Dorian #4 mode (fourth degree of the harmonic minor scale) generates the tensions 9th, #11th, and 13th.
DOMINANT 7th “Shell chord voicings”
C7 on the mid-lower strings [R 3 b7]
C7 on the middle strings w/ addb9 [R 3 b7 b9]
C7 on the middle strings w/ add9 [R 3 b7 9]
C7 on the middle strings w/ add#9 [R 3 b7 #9]
C7 on the lower strings w/ add#11 [R b7 3 #11]
C7 on the lower strings w/ addb13 [R b7 3 b13]
C7 on the lower strings w/ add13 [R b7 3 13]
The Mixolydian mode (fifth degree of the major scale) generates the tensions 9th and 13th.
The Lydian b7 mode AKA Mixolydian #4 mode (fourth degree of the melodic minor scale) generates the tensions 9th, #11th, and 13th.
The Mixolydian b6 mode (fifth degree of the melodic minor scale) generates the tensions 9th and b13th.
The Mixolydian b2b6 mode (fifth degree of the harmonic minor scale) generates the tensions b9th and b13th.
The Half-whole diminished scale AKA Dominant diminished scale generates the tensions b9th, #9th, #11th, and 13th.
The fourth degree remains an avoided note for dominant chords, as it is for all major chords. Although the dissonance between the third and fourth degrees may not be problematic, it does alter the chord's character.
HALF-DIMINISHED “Shell chord voicings”
Cmin7(b5) on the mid-lower strings [R b3 b7]
Cmin7(b5) on the middle strings w/ add9 [R b3 b7 9]
Cmin7(b5) on the lower strings w/ add11 [R b7 b3 11]
Cmin7(b5) on the lower strings w/ addb13 [R b7 b3 b13]
Cmin7(b5) on the lower strings w/ add13 [R b7 b3 13]
The Locrian mode (seventh degree of the major scale) generates the tensions 11th, and b13th.
The Locrian 2 mode (sixth degree of the melodic minor scale) generates the tensions 9th, 11th, and b13th.
***The Locrian 6 mode (second degree of the harmonic minor scale) generates the tensions 11th, and 13th.
DIMINISHED 7th “Shell chord voicings”
Cdim7 on the mid-lower strings [R b3 bb7]
Cdim7 on the middle strings w/ add9 [R b3 bb7 9]
Cdim7 on the lower strings w/ add11 [R bb7 b3 11]
Cdim7 on the lower strings w/ addb13 [R bb7 b3 b13]
Cdim7 on the lower strings w/ addb15 [R bb7 b3 b15]
The Symmetrical Diminished scale generates the tensions 9th, 11th, b13th, and b15th.
****Unlike most scales and modes, the symmetrical diminished scale is an octatonic scale that features an additional note, Cb (key of C), as its final degree. This Cb is classified as an available tension and is referred to as "addb15" due to its compound interval. While some musicians might label this note as a major seventh, choosing to call it B instead of Cb, this practice leads to confusion. This is because the diminished seventh chord already incorporates another seventh, namely, the Bbb (diminished seventh). For this reason, it is recommended to name it Cb.
MINOR MAJOR 7th “Shell chord voicings”
Cmin(maj7) on the mid-lower strings [R b3 7]
Cmin(maj7) on the middle strings w/ add9 [R b3 7 9]
Cmin(maj7) on the lower strings w/ add11 [R 7 b3 11]
Cmin(maj7) on the lower strings w/ add#11 [R 7 b3 #11]
Cmin(maj7) on the lower strings w/ add13 [R 7 b3 13]
The Melodic minor scale AKA Jazz minor scale generates the tensions 9th, 11th, and 13th.
*****The Melodic minor #4 scale AKA Jazz minor #4 scale generates the tensions 9th, #11th, and 13th.
DOMINANT 7th SUSPENDED 4th “Shell chord voicings”
C7sus4 on the mid-lower strings [R 4 b7]
C7sus4 on the middle strings w/ addb9 [R 4 b7 b9]
C7sus4 on the middle strings w/ add9 [R 4 b7 9]
C7sus4 on the middle strings w/ addb17 [R 4 b7 b17]
C7sus4 on the lower strings w/ add17 [R b7 4 17]
C7sus4 on the lower strings w/ addb13 [R b7 4 b13]
C7sus4 on the lower strings w/ add13 [R b7 4 13]
The Mixolydian mode (fifth degree of the major scale) generates the tensions 9th, 13th, and 17th.
The Dorian b2 mode (second degree of the melodic minor scale) generates the tensions b9th, 13th, and b17th.
The Phrygian mode (third degree of the major scale) generates the tensions b9th, b13th, and b17th.
The 17th is actually a major third while the b17th is a minor third. When it comes to 7sus4 chords, the 3rd is no longer considered a chord tone, but instead becomes an available tension. You may be wondering if adding the third will cause the chord to sound dissonant or change its quality. The answer is that it depends on how you add the tension. If the third is added above the fourth, a seventh interval will be created between the two, which is different than if it were done the opposite way. If the third is the lowest note of the chord and the fourth is above it, a minor 9th interval will result and create unwanted dissonance. Additionally, the further apart the third and fourth are from each other, the less tension there will be between them. This is why we refer to it as the 17th instead of the 10th, even though they are the same notes.
MAJOR 7th (#5) “Shell chord voicings”
Cmaj7(#5) on the mid-lower strings [R 3 7]
Cmaj7(#5) on the middle strings w/ add9 [R 3 7 9]
Cmaj7(#5) on the lower strings w/ add#11 [R 7 3 #11]
The Lydian #5 mode AKA Lydian augmented (third degree of the melodic minor scale) generates the tensions 9th and b13th.
MAJOR 7th (b5) “Shell chord voicings”
Cmaj7(b5) on the mid-lower strings [R 3 7]
Cmaj7(b5) on the middle strings w/ add9 [R 3 7 9]
Cmaj7(b5) on the lower strings w/ addb13 [R 7 3 b13]
Cmaj7(b5) on the lower strings w/ add13 [R 7 3 13]
The Lydian #5 mode AKA Lydian augmented (third degree of the melodic minor scale) generates the tensions 9th and b13th.
******The Lydian mode (fourth degree of the major scale) generates the tensions 9th and 13th.
DOMINANT 7th (#5) “Shell chord voicings”
C7(#5) on the mid-lower strings [R 3 b7]
C7(#5) on the middle strings w/ addb9 [R 3 b7 b9]
C7(#5) on the middle strings w/ add9 [R 3 b7 9]
C7(#5) on the middle strings w/ add#9 [R 3 b7 #9]
C7(#5) on the lower strings w/ add#11 [R b7 3 #11]
The Whole-tone scale generates the tensions 9th and #11th.
The Altered scale AKA Super Locrian and Altered dominant scale generates the tensions b9th, #9th, and #11th.
DOMINANT 7th (b5) “Shell chord voicings”
C7(b5) on the mid-lower strings [R 3 b7]
C7(b5) on the middle strings w/ addb9 [R 3 b7 b9]
C7(b5) on the middle strings w/ add9 [R 3 b7 9]
C7(b5) on the middle strings w/ add#9 [R 3 b7 #9]
C7(b5) on the lower strings w/ addb13 [R b7 3 b13]
C7(b5) on the lower strings w/ add13 [R b7 3 13]
The Whole-tone scale generates the tensions 9th and b13th.
The Altered scale AKA Super Locrian and Altered dominant scale (seventh degree of the melodic minor scale) generates the tensions b9th, #9th, and b13th.
The Half-whole diminished scale AKA Dominant diminished scale generates the tensions b9th, #9th, and 13th.
The Lydian b7 mode AKA Mixolydian #4 mode (fourth degree of the melodic minor scale) generates the tensions 9th and 13th.
MAJOR 6th “Shell chord voicings”
C6 on the mid-lower strings [R 3 6]
C6 on the middle strings w/ add9 [R 3 6 9]
C6 on the lower strings w/ add#11 [R 6 3 #11]
C6 on the lower strings w/ addb14 [R 6 3 b14]
C6 on the lower strings w/ add14 [R 6 3 14]
The Lydian mode (fourth degree of the major scale) generates the tensions 9th, #11th, and 14th.
The Lydian #2 mode (sixth degree of the harmonic minor scale) generates the tensions #9th, #11th, and 14th.
The Mixolydian mode (fifth degree of the major scale) generates the tensions 9th and b14th.
*******The 14th and b14th intervals are the major and minor sevenths, respectively. With the inclusion of the sixth in the chord's lower structure, the 14th is now a potential tension to add. However, it is important to note that adding the 14th will result in a chord with a major seventh sound and cannot be substituted for a dominant chord, for example.
MINOR 6th “Shell chord voicings”
Cmin6 on the mid-lower strings [R b3 6]
Cmin6 on the middle strings w/ add9 [R b3 6 9]
Cmin6 on the lower strings w/ add11 [R 6 b3 11]
Cmin6 on the lower strings w/ add#11 [R 6 b3 #11]
Cmin6 on the lower strings w/ add14 [R 6 b3 b14]
Cmin6 on the lower strings w/ add14 [R 6 b3 14]
The Dorian mode (second degree of the major scale) generates the tensions 9th, 11th, and b14th.
The Dorian #4 mode (fourth degree of the harmonic minor scale) generates the tensions 9th, #11th, and b14th.
The Melodic minor scale generates the tensions 9th, 11th, and 14th.
HOW TO PRACTICE SHELL CHORDS?
As we continue our exploration of chords, the advice provided in the previous three articles (Triads, Drop-2 Chords, Drop-3 Chords) is still relevant to this topic. However, you’ve probably noticed I haven't discussed inversions in this article and the reason is because the shell chord inversions are not very practical. The advantage of using shell chords is that we can add different tensions to them and explore a wide range of colors for every chord. In this article, I'll provide more examples of how to apply these chords to songs, some of which are similar to the exercises we have already covered.
1) Choose a different chord quality every day and experiment with playing the Cmin7 shell voicings on various strings. Can you play the minor seventh shell voicing in all twelve keys? What about additional chords like Cmin7(add9), Cmin7(add11), Cmin7(add#11), or Cmin7(add13)? How about the other 7th-chord types and extensions? Practicing this exercise will enhance your instrument fluency.
2) Attempt to play songs you already know but in different ways. You can find the same chords in other regions of your instrument, creating more engaging chord progressions. There is no "correct" way to choose which voicings to use; any combination is valid. Ultimately, it is your arrangement, song, and voicings!
The following images show the Shell chord voicings applied to the four first measures of Autumn Leaves: (Cmin7 | F7 | Bbmaj7 | Ebmaj7).
[Four first measures of Autumn Leaves in shell chords on the higher and mid-higher strings]
[Four first measures of Autumn Leaves in shell chords on the mid-higher and mid-lower strings]
[Four first measures of Autumn Leaves in shell chords on the mid-lower and lower strings]
The following image show the Shell chord voicings applied to the four first measures of Autumn Leaves adding 9ths to each chord: (Cmin7 | F7 | Bbmaj7 | Ebmaj7).
[Four first measures of Autumn Leaves in shell chords on the mid-higher and mid-lower strings]
The following image show the Shell chord voicings applied to the four first measures of Autumn Leaves combining 9ths and 11ths to each chord: (Cmin7 | F7 | Bbmaj7 | Ebmaj7).
[Four first measures of Autumn Leaves in shell chords on the mid-lower and lower strings]
These combinations are frequently used by many guitarists, and you should incorporate them into your playing. However, don't forget to be creative and develop your own voicings. Try playing all the chords with add11, or add13. Experiment with different extensions for each chord. Can you play a different extension for every chord? Try it out and let me know!
Furthermore, I have written an eBook with over 140 pages that covers all the 7th-chords mentioned in this article in every set of strings and with all available tensions in all 12 keys. You can find this eBook by clicking on the link below or visiting the "STORE" section. This book is not a replacement for the previous exercises but rather a comprehensive reference to help guide your practice.
All of these theory concepts are available for free on my blog to anyone interested in learning more about music. However, producing this content is time-consuming, so if you found this article helpful, please consider purchasing the material to support the blog or joining our membership plan (available in April 2023). Through weekly videos, I will teach different applications for all this material, and I will answer all your questions.
You can also follow me on Instagram @_rodrigodmoreira for weekly quizzes to test your comprehension on these topics and suggest more ideas for future articles!
All my best,