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Should You Learn Music Theory?  - Part 3

April 22, 20236 min read

Welcome to the Freteleven blog! If this is your first time visiting, we're glad to have you here, and if you're already a part of our community, welcome back. I hope our discussions on music theory and its application to the guitar have been both engaging and beneficial for you. I understand that for some, the idea of learning music theory can seem overwhelming and unrelated to improving one's playing ability.

Traditionally, music theory has been taught as an academic exercise, often focused on passing tests and then quickly set aside for more thrilling pursuits, without ever truly connecting to the fretboard or how we hear music. However, the real value of learning music theory lies in knowing the elements so well that it becomes effortless to think about them. This effortless awareness allows you to fully immerse yourself in your musical expression without any distractions.

If you're committed to incorporating music theory into your guitar playing, stick with me through this series, and you'll be well on your way to making theory a tool for expressing your ideas on the guitar.

In our last post (Should You Learn Music Theory? - Part 2), we delved into the concept of spelling triads, providing you with a practical method to learn the notes in any triad. Today, we'll build on that foundation by learning to spell 3rds and 6ths.

I want to revisit the goal and benefits of learning how to 'spell' different elements in music theory. In the first post of this series (Should You Learn Music Theory - Part 1), we established a foundation by learning the major scales and focusing on quick recall. As we progress through the series, we'll build upon that knowledge to understand the inner harmony of a given key. Spelling triads and intervals is an approach that emphasizes patterns that aren't tied to any specific key. These patterns are easy to identify and learn, thanks to their consistency.

Mastering the ability to spell various musical elements is crucial for instantly recalling them while playing. This skill not only puts more extensive elements, like major or minor keys, into context but also makes them easier to learn. By honing your spelling abilities, you'll be well-equipped to navigate the world of music theory and enhance your guitar-playing experience.

If You Are New to Intervals

When spelling thirds and sixths, it's important to include the correct number of letter names to represent the interval properly.

For thirds, the interval includes three letter names. For example, C to E is a major third because it includes three letter names: C, D, and E . This accurately represents the structure of the interval, which spans two whole steps or four semitones. Using the proper letter names helps maintain consistency in music theory and makes it easier to understand and communicate musical ideas.

Similarly, for sixths, the interval includes six letter names. For instance, C to A is a major sixth because it includes six letter names: C, D, E, F, G, and A. This accurately represents the structure of the interval, which spans four and a half whole steps or nine semitones. Just like with thirds, using the correct letter names is essential for consistency and clarity in music theory.

Using the appropriate letter names when spelling thirds and sixths ensures that the intervals are accurately represented, making it easier for musicians to recognize, interpret, and perform these intervals when reading sheet music.

Maj Third and Major Sixth Core Intervals

Much like learning to spell triads, we'll start with a core set to simplify and base everything else on. This allows you to quickly learn these intervals. This is the most important step when learning thirds and sixths. Become completely familiar with the core interval spellings before moving on for the quickest benefit.


A major third interval is two notes that are two whole steps or 4 semi-tones apart.

Thirds and sixths spellings


A major sixth interval is two notes that are four and a half whole steps or 9 semi-tones apart.

Sixths Spellings

Grouping the Intervals Visually

Continuing on in much the same way we did with triads in the last post, it is very easy to take the core intervals and find a third or a sixth up from any note.


Thirds 2Thirds 3


Sixths 2Sixths 3

min thirds and min sixths

Now that you're familiar with major 3rds and major 6ths, let's explore how to quickly find their minor counterparts, the minor 3rds and minor 6ths. To convert a major 3rd to a minor 3rd, simply lower the top note of the interval by one semitone (half step). For example, if you have a major 3rd interval of C to E, lowering the E by one semitone will result in a minor 3rd interval: C to E♭. A minor 3rd is a 1/2 step smaller than a major 3rd, giving it a different sound.

Similarly, to convert a major 6th to a minor 6th, lower the top note of the interval by one semitone. For instance, if you have a major 6th interval of C to A, lowering the A by one semitone will give you a minor 6th interval: C to A♭. A minor 6th is a 1/2 step smaller than a major 6th, also giving it a different sound.

By practicing these conversions, you will quickly be able to find minor 3rds and minor 6ths from their major counterparts, giving you a versatile range of intervals to use in your playing. These skills will not only help you better understand the relationships between notes but also open up new creative possibilities for your guitar playing.

Train Relentlessly Until the Need for Practice Disappears

There are several effective methods for practicing the spelling of thirds and sixths, but one particularly useful approach is the interval grid exercise. Similar to the triad grid exercise discussed in our previous post (Should You Learn Music Theory - Part 2), this exercise uses a 2x2 grid. At the top of the grid, indicate which interval you are practicing: Maj 3 = R-3, min3 = R-♭3, Maj 6 = R-6, and min6 = R-♭6.

Each grid poses two questions. For example, if the note in the diagonal is C and the interval is a major 6th (R-6), the two questions would be:

  1. What is the major 6th up from C?

  2. What is the major 6th down from C?

To practice, print out the grid exercise and fill in the blanks. By this stage, you should be able to recall the answers from the patterns above without having to "figure them out" step by step..

Spelling worksheet 1

I'd love to hear your questions or feedback. Please feel free to reach out anytime at, and I'll be happy to respond.

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Andrew Gingerich

freteleven founder

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