• The 7-Chord: The Most Dissonant Chord In The Major Key

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    The most dissonant chord in the major key that is rarely used is the 7-chord and in this lesson I’ll tell you why.

    The term dissonant here is used to describe the unpleasantness of the 7-chord and describing the 7-chord as the most dissonant chord in the major key means that the 7-chord is the most unpleasant chord in the major key.

    Before I go ahead and tell you why the 7-chord is the most dissonant chord in the major key, let’s invest the next segment into refreshing our minds on the 7-chord in the major key.

    A Quick Review On The 7-chord In The Major Key

    The chord of the 7th tone of the scale in any key is known as the 7-chord and this is derived from a number system where chords are associated with numbers.

    In the number system, every tone of the C major scale:

    …is associated with numbers, starting from C which is associated with 1:

    C is 1

    D is 2

    E is 3

    F is 4

    G is 5

    A is 6

    B is 7

    The 7-chord is the chord of the seventh tone of the C major scale (which is B):

    …and can either be a triad or a seventh chord:

    Triad (B diminished triad):

    Seventh chord (B half-diminished seventh chord):

    “How To Find The 7-chord In Any Key…”

    Go a half-step below the first tone in any key you’re in and form a diminished triad or a half-diminished seventh chord and you’ll have the 7-chord.

    In the key of D major:

    …a half-step below D (which is the first tone in the key):

    …is C#:

    So, C# diminished triad and C# half-diminished seventh chord:

    C# diminished triad:

    C# half-diminished seventh chord:

    …are 7-chord options in the key of D major.

    The Dissonance Of The 7-chord — Explained

    The major key is populated with common chords and they are either of a major or minor quality: the 1-chord, 2-chord, 3-chord, etc., are all common chords and they are NOT dissonant.

    Let’s discuss briefly on common chords.

    A Short Note On Common Chords

    When the interval between the root and fifth tone of a chord is a perfect fifth, such a chord is said to be a common chord.

    In the key of C major:

    …where the 1-chord is the C major triad:

    …the interval between the root and fifth tone (which are C and G respectively):

    …is a perfect fifth interval.

    The 7-chord Is Not A Common Chord

    The only chord that stands out in the major key is the 7-chord and this is because every other chord is a common chord. A closer look at the B diminished triad:

    …which is the 7-chord in the key of C major, you’ll notice that the interval (or distance) between its root and fifth tone (which are B and F respectively):

    …is a diminished fifth.

    The diminished fifth interval between the root and fifth tone of the 7-chord makes the 7-chord sound unstable, unpleasant, and dissonant.

    Final Words

    The primary reason why the 7-chord is the most dissonant chord in the major key is because it is NOT a common chord.

    The 7-chord is rarely used in the major key and when used, it functions as an incomplete dominant chord and we’ll be looking at the relationship between the 7-chord and the dominant chord in another lesson.

    All the best!

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    Chuku Onyemachi

    Head of Education at HearandPlay Music Group
    Onyemachi "Onye" Chuku is a Nigerian musicologist, pianist, and author. Inspired by his role model (Jermaine Griggs) who has become his mentor, what he started off as teaching musicians in his Aba-Nigeria neighborhood in April 2005 eventually morphed into an international career that has helped hundreds of thousands of musicians all around the world. Onye lives in Dubai and is currently the Head of Education at HearandPlay Music Group and the music consultant of the Gospel Music Training Center, all in California, USA.




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