Building 7th Chords: Major, Minor, and Dominant

Hello! Welcome back.

In our last lesson, you did a great job moving from the theory of triads to the practical application of building and playing them on the fretboard. We established that major and minor triads are the foundational three-note chords (Root, 3rd, 5th) and that you can find them by altering shapes you already know.

Today, we're going to add another layer of color to our harmonic palette. We'll be expanding our triads into four-note chords, which are central to the sound of rock, blues, and countless other genres. Your goal for this lesson is to explain the construction of major 7th, minor 7th, and dominant 7th chords. This is a crucial step in understanding the "why" behind the rich and emotionally complex sounds you hear in music.

Part 1: From Triads to Seventh Chords

A seventh chord is, quite simply, a triad with an added seventh. Just as we built triads using the 1st, 3rd, and 5th notes of a scale, we now add the 7th note. This fourth note adds a new dimension of character to the chord.

However, things get interesting because there are two main types of "seventh" interval we need to know:

The Major 7th (M7): This is the 7th note directly from the major scale. A very practical way to find it on the guitar is to locate your root note and go down one half-step (one fret). For example, the major 7th of C is B.
The minor 7th (m7 or ♭7): This is a flattened major 7th. To find it, you go down one whole-step (two frets) from your root note. For example, the minor 7th of C is B♭.

A common point of confusion is the naming convention. When a chord symbol just says "7" (like G7), it implies a minor 7th interval. When the chord has a major 7th interval, the symbol will explicitly say so (like Gmaj7).

This short video gives a great overview of this concept.

7th CHORDS On Guitar Explained [Music Theory And Practice]

In this video, '7th CHORDS On Guitar Explained' from MusicTheoryForGuitar, the instructor clearly defines the Major 7th and minor 7th intervals relative to the root note.

Watch the first 1 minute and 30 seconds. Pay close attention to how the Major 7th is defined as one half-step below the root, and the minor 7th as two half-steps below the root. This is a very useful guitar-centric way to think about it.

Part 2: The Three Essential Seventh Chords

Now, let's combine these two types of sevenths with the major and minor triads we already know. This gives us three essential seventh chords, each with a unique formula and a distinct emotional character.

For consistency, let's use C as our root note for all examples.

C Major Triad: C - E - G
C minor Triad: C - E♭ - G

1. The Major Seventh Chord (maj7)

This chord is often described as sounding "dreamy," "sophisticated," or "relaxed."

Formula: Major Triad + Major 7th
Intervals: Root – Major 3rd – Perfect 5th – Major 7th (R - M3 - P5 - M7)
Example (Cmaj7): We take a C Major triad (C-E-G) and add a Major 7th (B). The resulting notes are C – E – G – B.

2. The Dominant Seventh Chord (7)

This is the sound of the blues. It's full of tension and has a strong desire to resolve, making it feel "bluesy," "powerful," and "unstable."

Formula: Major Triad + minor 7th
Intervals: Root – Major 3rd – Perfect 5th – minor 7th (R - M3 - P5 - m7)
Example (C7): We take a C Major triad (C-E-G) and add a minor 7th (B♭). The resulting notes are C – E – G – B♭.

3. The Minor Seventh Chord (m7)

This chord has a "mellow," "soulful," or "reflective" quality. It's smoother than a dominant 7th but moodier than a major 7th.

Formula: minor Triad + minor 7th
Intervals: Root – minor 3rd – Perfect 5th – minor 7th (R - m3 - P5 - m7)
Example (Cm7): We take a C minor triad (C-E♭-G) and add a minor 7th (B♭). The resulting notes are C – E♭ – G – B♭.

The following reading provides a great summary of these chord types, their formulas, and their characteristic sounds.

Dominant 7 vs maj7 vs m7 Chords - Differences & Use Cases

The article 'Dominant 7 vs maj7 vs m7 Chords' by Audible Genius breaks down the construction of each chord with clear note examples.

Read the first section, 'Dominant 7 vs maj7 vs m7 – What’s The Difference?'. Focus on the specific notes listed for C7, Cmaj7, and Cm7, and how they relate back to the triad and seventh formulas we just discussed.

This chart provides a fantastic visual breakdown of these formulas in action, showing how different 7th chords are built using notes from the C major scale. For now, focus on the CMaj7, Dm7, and G7 chords in the chart to see the interval patterns we've discussed.

7th Chords of the C Major Scale — This chart illustrates how 7th chords are constructed. Notice the interval structure for each chord type: CMaj7 uses a Major 3rd and Major 7th, Dm7 uses a minor 3rd and minor 7th, and G7 (a dominant chord) uses a Major 3rd and minor 7th.

Part 3: From Theory to Fretboard Logic

While our main goal today is understanding the theory, it's helpful to see how this construction applies logically on the guitar. Just as you learned to create a minor triad by lowering the 3rd of a major triad, you can create 7th chords by altering the root note of a familiar chord shape.

Let's watch a clear demonstration of this idea.

It makes you sound better: SEVENTH CHORDS! Music Theory ep. 6

In this clip from Paul Davids, he demonstrates a very practical way to build these chords on the fly, starting from a simple D major chord. This reinforces the theory of construction in a hands-on way.

Watch from 04:48 to 07:15. First, see how he transforms a D major chord into a Dmaj7 and then a D7 by lowering the octave (root) note on the B string. Next, notice how he applies a similar logic starting from a D minor chord to create a Dm7. This method of modifying a known shape is a powerful tool for understanding chord construction.

This exercise connects the abstract formulas directly to a physical action on the fretboard. By finding a root note in a chord and moving it down by one or two frets, you are manually applying the M7 and m7 intervals to build these new sounds.

Conclusion

Excellent work today. You've now unlocked the theory behind the four-note chords that form the backbone of blues, rock, and jazz. Moving beyond triads gives your playing access to a much wider range of emotional expression.

Key Takeaways:

Seventh chords are triads plus a seventh note.
The two key intervals are the Major 7th (one fret below the root) and the minor 7th (two frets below the root).
The construction formulas are systematic:
- Major 7th (maj7): Major Triad + Major 7th (R-M3-P5-M7)
- Dominant 7th (7): Major Triad + minor 7th (R-M3-P5-m7)
- Minor 7th (m7): minor Triad + minor 7th (R-m3-P5-m7)
These chords have distinct sounds: maj7 is relaxed, 7 is tense and bluesy, and m7 is mellow and soulful.

Preview of the Next Lesson:

We've repeatedly referenced how these chord tones come from scales. To truly master harmony and prepare for improvisation, we need a strong command of the scales themselves. In our next lesson, we will construct the natural minor scale and explain its relationship to the relative major key. This will open the door to understanding how different scales and chords fit together within a single key.

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