Musical Building Blocks – Creating Melodies with Tetrachords
Updated: Oct 29, 2019
Just as DNA is made up of the building blocks (nucleotides) that tell cells how to make up organisms, there are building blocks that make up the scales we use in music. Music starts with individual notes that are strung together like DNA into groups that create musical "chords" or lines. Don't let the term "chord" confuse you, chord comes from the Greek χορδά (khordá) which literally means string. Originally, when musicians talked about chords, they were referring to the number of strings that their zither (harp) had. A group of two notes is called a duochord (or an interval). A group of three notes is called a trichord. Four notes form a tetrachord. Five, a pentachord (or pentatonic scale). Six, a hexachord (or hexatonic scale), and seven is a heptachord (or heptatonic scale). Our Western Major and Minor scales fall into this last category. There are others, but that's enough for now. For today, we are focusing on creating melodies with tetrachords.
For this lesson, some previous knowledge of scales, intervals, and musical steps is very helpful. If musical steps are new to you, you can visualize a piano keyboard or a guitar where a half step is two frets on the same string or pIano keys that are right next to one another and a whole step has one fret or key between it. For example, A to B is a whole step and A to B♭is a half step.
A tetrachord is a series of four notes; the interval between the first and last notes spans no further than a tritone or six-half steps.
A tetrachord is a series of four notes; the interval between the first and last notes spans no further than a tritone or six-half steps. Tetrachords can be thought of as making up half a Western scale. Two tetrachords can be strung together to form an eight-note-long major or minor scale. When two tetrachords are linked together to create a scale, they are referred to as "Tetrachord I" and "Tetrachord II" respectively. Though there are many variations of tetrachords that can be built. First, we will focus on how tetrachords are used to build Western major and minor scales. Then we will complete a melody building activity using tetrachords. Lastly, we will discuss some other common tetrachords that you can add to your music practice.
Tetrachords may be an unfamiliar concept to even some experienced musicians. I was unaware of them until I studied guitar even though I had studied piano and voice for years previously. However, they are a common topic that guitarists and bassists to study because understanding them facilitates improvisation skills and the patterns they form fit well under a guitarist or bassist's fingers. Such string players often start their improvisation studies with tetrachords. But, they are for more than just guitar and bass players as they make a great building block for improvising, composing, and technical practice for all instruments and even the voice. All musicians will benefit from creating their own warm-ups with tetrachords and flexing their improvisational muscles.
Building Major and Minor Scales with Tetrachords
As we mentioned before, Western major and Minor Scales are built of tetrachords. When two tetrachords are linked together to create a scale, they are referred to as "Tetrachord I" and "Tetrachord II" respectively. The graphic below shows the tetrachords that make up major and minor scales starting on the pitch "C." To build other major and minor scales, you would take the same half and whole step patterns as though shown below but start them on the desired pitch.