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Should You Learn Music Theory?  - Part 4

April 29, 20237 min read

Welcome back to the Freteleven blog! If you're new here, I'm delighted to have you join our community. Over the past few weeks, I've explored music theory and its application to the guitar in our series "Should You Learn Music Theory?" My goal is to help you understand music theory in a way that directly impacts your guitar playing, making it more enjoyable and intuitive and actually worth learning.

In my previous post (Should You Learn Music Theory? - Part 3), I tackled the concept of spelling 3rds and 6ths, equipping you with a practical method to learn these intervals. Today, I'll expand on that foundation by teaching you how to spell 4ths and 5ths, starting with diatonic 4ths and 5ths, and then moving on to diminished and augmented 4ths and 5ths.

Before we take a look at 4ths and 5ths, just a reminder that the true power of music theory lies in mastering it to the point where it becomes an intuitive part of your creative process, allowing you to express yourself effortlessly when playing, performing, or composing. By learning music theory to 100%, you develop a deep familiarity with the fundamental elements of music, which in turn enables you to internalize these concepts and use them instinctively in your daily playing. When music theory becomes second nature, much like walking or breathing, you no longer need to "figure things out" consciously. Instead, your understanding of harmony, melody, and rhythm will flow naturally, empowering you to create more dynamic, engaging, and emotive musical experiences.

If You Are New to Intervals, 2 when spelling 4ths and 5ths, it's important to include the correct number of letter names to represent the interval accurately.

For 4ths, the interval includes four letter names. For example, C to F is a fourth because it includes four letter names: C, D, E, and F. The term "perfect" in "perfect fourth" refers to the specific quality of the interval in relation to its sound; both notes are in the diatonic scale. A perfect fourth spans two and a half whole steps or five semitones. Using the proper letter names helps maintain consistency in music theory and makes it easier to understand and communicate musical ideas.

Similarly, for 5ths, the interval includes five letter names. For instance, C to G is a fifth because it includes five letter names: C, D, E, F, and G. The term "perfect" in "perfect fifth" also indicates the specific quality of the interval in relation to its sound; both notes are in the diatonic scale. This accurately represents the structure of the interval, which spans three and a half whole steps or seven semitones. Just like with all intervals, using the correct letter names is essential for consistency and clarity in music theory.

Perfect Fourth and Perfect Fifth Core Intervals

Perfect Fourths

A perfect fourth interval is two notes that are 2.5 whole steps or 5 semi-tones apart.

Fourth spellings 1

Perfect Fifths Core Interval Spellings

A perfect fifth interval is two notes that are 3.5 whole steps or 7 semi-tones apart.

Fifths Spellings 1

Grouping the Intervals Visually

With little effort it is easy to spell any perfect fourth or perfect fifth.


Fourths Spelling 2Fourth Spellings 3


Fifth Spellings 3Fifth Spellings 4

Diatonic, Diminished, and Augmented 4ths and 5ths

Altered fourths and fifths, which include diminished and augmented intervals, are modifications of the perfect fourth and perfect fifth intervals. These alterations change the distance between the two notes, either by expanding or contracting it, resulting in a different sound and harmonic quality. To spell a diminished fourth, you need to decrease the distance of a perfect fourth by one semitone. For example, starting with a perfect fourth interval of C to F, lowering the F by one semitone results in a diminished fourth interval of C to F♭. In contrast, to spell an augmented fourth, you increase the distance of a perfect fourth by one semitone. Using the same C to F perfect fourth interval, raising the F by one semitone results in an augmented fourth interval of C to F♯.

Similarly, for altered fifths, you can create a diminished fifth by decreasing the distance of a perfect fifth by one semitone. For instance, starting with a perfect fifth interval of C to G, lowering the G by one semitone results in a diminished fifth interval of C to G♭. Conversely, to spell an augmented fifth, you increase the distance of a perfect fifth by one semitone. Using the same C to G perfect fifth interval, raising the G by one semitone results in an augmented fifth interval of C to G♯. Understanding and practicing the spelling of altered fourths and fifths will provide you with a greater range of harmonic possibilities and contribute to a more versatile musical vocabulary.

The 'Tri-Tone'

A tritone is a unique and important interval in music theory, which is also referred to as an augmented fourth or diminished fifth. Spanning three whole steps or six semitones, the tritone sits exactly halfway between the octave, creating a dissonant and tense sound. For example, a tritone from C would be either F♯ (augmented fourth) or G♭ (diminished fifth), as both of these notes are equidistant from C within the octave.

The tritone's importance stems from its distinctive harmonic qualities and its role in various musical contexts. Historically, the tritone was known as the "devil's interval" due to its dissonance and was often avoided in sacred music. However, in modern music, the tritone is used to create tension and resolve it, which is an essential aspect of many compositions and genres, especially in jazz and blues.

One notable example of the tritone's significance is its presence in dominant seventh chords, where the tritone interval is formed between the major third and the minor seventh. This interval creates a strong desire for resolution, making the dominant seventh chord a driving force in functional harmony, as it naturally wants to resolve to the tonic chord. The tritone is also the basis for tritone substitution, a common technique in jazz, where a dominant chord is replaced with another dominant chord whose root is a tritone away, creating a smooth and surprising voice leading.

In summary, the tritone's unique sound and its ability to create tension and resolution make it an essential interval in music and an important sound in many styles.

Train Relentlessly Until the Need for Practice Disappears

There are several effective methods for practicing the spelling of 4ths and 5ths, but one particularly useful approach is the interval grid exercise. Similar to the grid exercises discussed in my previous posts (Should You Learn Music Theory - Parts 2 and Part 3), this exercise uses a 2x2 grid. At the top of the grid, indicate which interval you are practicing: P4 = R-4, Aug4 = R-♯4, dim5 = ♭5, P5 = R-5, and so on.

Each grid poses two questions. For example, if the note in the diagonal is C and the interval is a perfect 5th (R-5), the two questions would be:

The first question (in the first row of the grid) would be, what is the perfect 5th up from C?

The second question (in the second row of the grid) would be what is the perfect 5th down from C?

To practice, print out the grid exercise below 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.

Interval Worksheet

As with any new skill, consistent practice is essential for mastering interval spelling. Make it a point to practice regularly until the need for conscious effort disappears, and you can quickly and accurately spell 4ths and 5ths without hesitation. This ability will help you better understand the relationships between notes and open up new creative possibilities for your guitar playing.

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

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