A. The Shell and Chord Theory

Introduction

As a jazz pianist, one of the main jobs that you have is to play the harmony to support the melody instruments. To do this, you need to understand how chords work.

Basic Chord Theory

The first way that you should understand chords is by stacking thirds in root position (meaning that the lowest note is the root note). Below is a chart to help you visualize all the possible notes in a chord. The most important kinds of chords to know are the ones in bold below (labelled I, ii, and V), being able to play the root, 3rd, and 7th of the chord. The 3rd and 7th played together is known as The Shell. The Shell defines the quality and function of the chord (major, minor, or dominant) and you do not need any other notes to get that idea across. You may choose to add notes to alter or color the chord, but that will not change its identity as major, minor, or dominant.

Each note in a chord is assigned a number, and when you build chords in thirds, each number is odd starting at 1 and ending at 13. The notes 1, 3, 5, and 7 are the basic structure to the chord. The notes 9, 11, and 13 are Upper Extensions and add color to the chord. The upper extensions (and the 5th) are sometimes altered (sharpened or flattened), especially on dominant chords for good voice leading and coloration.

In the sheet music below, check out how to build major, minor, and dominant chords by stacking thirds. Most importantly, scroll down to see the Root + Shell (3rd and 7th, in root position) to see what notes are in each chord.

When you actually play these chords in a song, learn to voice them in many different ways.

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Jazz_Chord_Construction.pdf

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Jazz Chord Construction

Simplifying Complicated Chords

Now, even though we are focusing on playing the shell (root, 3, 7) right now, as you play songs, you might encounter chords that have extensions or look different. Here's how to replace some of those chords with simple major, minor, and dominant seven chords.

Simplifying chords into groups of major, minor, and dominant is a useful skill for pianists of all skill levels because knowing the quality will influence the substitutions, scales, sounds, and most importantly the function of what you play.

Chord	Replacement 7th chord (shell)
D9, D11, D13	D7 (dominant)
F6, F6/9, Fmaj9, Fmaj13	Fmaj7 (major)
Am6, Am6/9, Am9, Am11, Am13	Am7 (minor)

Diminished and augmented chords alter the fifth of the chord, so if you do these replacements, ensure that you do not include the fifth unless you properly alter it.

Chord	Replacement 7th chord (shell)
Caug (aka C+, augmented)	C7 (dominant)
Bm7b5 (aka B𝆩, half-diminished)	Bm7 (minor)
Edim (aka E°, diminished)	C7 (dominant) The root with the dim chord becomes the 3rd of the dominant chord.

Finally, any chords with altered upper extensions attached to them can be reduced by dropping the alterations.

Chord	Replacement 7th chord (shell)
D7#11, D7b9, D7#9#5, etc.	D7 (dominant)

Playing The Shell in a ii-V-I

The first way to practice jazz chords is by playing the shell, which is the 3rd and 7th of the chord.

Major ii-V-I

The progression outlined below is called a Major$ii$-$V$-$I$(or just$ii$-$V$-$I$, pronounced 2, 5, 1). The$ii$chord is minor, the$V$chord is dominant and the$I$chord is major. In the sheet below, the six ($VI$) chord is optional; you may play it if you want to repeat the measure to take you back to the$ii$chord.

1. Practice the shell in the right hand by itself.

2. Practice playing the shell in the right hand with the root in the left hand to internalize the sound of these chords with a bassist.

3. Practice playing the shell in the left hand by itself.

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Two note major_ii_V_I_(VI).pdf

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Major ii V I (shell)

Minor ii𝆩-V-i

Do the same practice routine as the major ii-V-I for the minor ii𝆩-V-i below.

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Two note minor_ii_V_I_(VI).pdf

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Minor ii𝆩-V-i (shell)

Learning Tunes

When you take your new-found harmony skills and decide to learn some tunes, here is a four-step process to mastering that tune. For each step, practice with a metronome and practice hands separately as needed.

1. Melody (RH) + Bass line roots only (LH).

2. Shell (RH) + Bass line roots only (LH).

3. Melody (RH) + Shell (LH).

4. Melody + Shell + Bass (spread across hands).

The first two steps are to help you understand the song and hear how the harmony and melody works together. The third and fourth steps are especially useful for solo piano practice and preparing to improvise over the tune.