Understanding Chord Structure: Triads, Seventh Chords, and Extended Chords


Music, like any other language, has its own unique set of structures and rules that allow it to be understood and appreciated by those who are familiar with it. One of the fundamental elements of music is chords. Understanding chord structure is crucial for any musician, whether you are a beginner just starting to learn an instrument or a seasoned professional looking to expand your harmonic knowledge. In this article, we will explore the different types of chords and their construction, from basic triads to extended chords, to help you better understand the complex world of chordal harmony.

Triads are the most basic type of chord in Western music, consisting of three notes stacked on top of each other. They are typically made up of the first (root), third, and fifth scale degrees of a particular key. For example, in the key of C major, a C major triad would consist of the notes C, E, and G. Each note in a triad has a specific function, with the root providing the foundation, the third giving the chord its major or minor quality, and the fifth adding stability and color. In each key, there are three major triads (built on the first, fourth, and fifth degrees of the scale) and three minor triads (built on the second, third, and sixth degrees).

Seventh chords, as the name suggests, consist of four notes and are created by adding a seventh scale degree to a triad. This extra note adds a new layer of complexity and character to a chord, making it richer and more interesting. Similar to triads, there are three types of seventh chords: major sevenths, dominant sevenths, and minor sevenths. A major seventh chord is formed by taking a major triad and adding a major seventh on top, while a minor seventh chord is created by adding a minor seventh to a minor triad. A dominant seventh chord has a slightly different formula, with a major triad and a minor seventh. These chords have an important role in jazz and popular music, and they add color and tension to a piece of music.

As musicians, we are always seeking to expand our harmonic vocabulary, and that is where extended chords come into play. These chords consist of five or more notes and are created by stacking thirds on top of a triad or seventh chord. The most common extended chords are ninth, eleventh, and thirteenth chords. A ninth chord is formed by adding a ninth scale degree to a seventh chord, while an eleventh chord adds the eleventh degree. Finally, a thirteenth chord consists of the first, third, fifth, seventh, ninth, and thirteenth scale degrees. These chords are often used in jazz, and they create a rich and complex sound that goes beyond the traditional triads and seventh chords.

Understanding chord structure is essential not only for playing music but also for composing and arranging. By knowing the different types of chords and their functions, you can create interesting and sophisticated harmonic progressions that will elevate your music to a new level. To give you a practical example, let us look at the chord progression of the popular song “Don’t Stop Believin'” by Journey. The verse of the song starts with a C major triad, then moves to a dominant seventh chord on G, adding tension and leading to a subtle resolution on a minor seventh chord, A minor. This progression uses the basic triads and seventh chords, but it creates a catchy and effective melody that everyone can sing along to.

In conclusion, chord structure is a crucial aspect of music theory that every musician should understand. From the building blocks of triads to the complexity of extended chords, each type of chord has a unique function and adds a different layer of emotion and color to a piece of music. By expanding your knowledge of chord construction, you will not only become a better musician but also a more versatile and creative one. So, keep practicing and exploring the world of chords, and you will be amazed at the endless possibilities they offer.