Practical Music Theory unit 8: Chord Scales (7th chords)

    Video:

  • Chord Scales (7th chords)

  • Chord Scales: 7th Chords

    We can extend the chord scale concept a step further by using the major scale to build seventh chords (you may want to refer back to the lesson on 7th chords for a refresher).  Again we’ll do the examples in this lesson in the key of C major, knowing that we can apply all of these concepts to any key.

    I chord:  maj7

    We’ll start the same way we did in the previous lesson, by building a chord off of the first degree of the scale.  But this time, instead of just building a triad, we take it one step further and add a fourth note to the chord.

    I7-chord

    We know, based on the information in the lesson on 7th chords, that if we take the 1st, 3rd, 5th, and 7th degrees of a scale and leave them as-is (not sharped or flatted), we get a major7 chord.  Therefore, the I chord in the key of C, when extended to a seventh chord, would be a Cmaj7.

    II chord: m7

    Starting from the second step of the scale (D), we get the following:

    II7-chord

    The chord contains the notes D, F, A, and C.  If we refer to the table of major scales and compare this to what we see in the D major scale (which contains an F# and a C#), we can see that the 3rd and 7th have been flatted–instead of F# and C#, we have an F and a C.  This means we have a minor7 chord.  Therefore we can say that the II chord in the key of C is a Dm7.

    III chord: m7

    Starting on the third step of the scale, here’s what we come up with:

    III7-chord

    If we take these notes, E G B D, and compare them with what we see in the E major scale (which contains a G# and a D#), we can see again that the 3rd and 7th are flatted, so again we have a minor7 chord.  Therefore the III chord in the key of C would be an Em7.

    IV chord: maj7

    Now we start on the fourth step of the scale:

    IV7-chord

    If we take these note, F A C E, and compare them to what we’d get the F major scale, we can see that we’d have virtually the same thing–F A C E.  Nothing is sharped or flatted.  Therefore we know that it is a major7 chord, and we can say that the IV chord in the key of C is an Fmaj7.

    V chord: dominant 7

    Now let’s build a 7th chord starting on the 5th step of the scale:

    V7-chord

    Taking these results, G B D F, and comparing them to a G major scale, we can see that the 7th is flatted (a G major scale has an F#, not an F).  Based on our lessons in chord construction, we know that a natural 3rd and a flatted 7th together make a dominant seventh chord.  Therefore we can say that the V chord in the key of C would be a G7 chord.

    How the dominant 7th chord got its name: Incidentally, the 5th step of a scale is, in formal music theory, known as the “dominant” (you may also have heard of the “tonic,” which is the I, or root, and the sub-dominant, which is the IV, though these terms have become a bit archaic and don’t get used that much any more outside of music theory classrooms).  That’s why the type seventh chord that we get when we build from this step is known as the “dominant seventh”.

    VI chord: minor7

    OK we’re getting close to the end here…hang in there for a couple more minutes.
    If we build a chord from the 6th step of the scale, we get the following:

    VI7-chord

    If we take these notes, A C E G, and compare them to what we’d see in an A major scale for reference, we can see again that the 3rd and 7th are flatted (A major would contain a C# and a G#).  Therefore we have another m7 chord, and we can say that the VI chord in the key of C would be an Am7 chord.

    VII chord: m7b5 or “half-diminished”

    Last, and possibly also least (certainly least common, anyway), we build a chord from the 7th step of the C major scale:

    VII7chord

    If we compare this, B D F A, to a B major scale, we can see that the 3rd, 5th, and 7th have ALL been flatted (B major would have a D#, F#, and A#).  This gives us a m7b5 chord, sometimes called a half-diminished chord.  So the VII chord in the key of C would be a Bm7b5.  Note that you won’t see this chord very often outside of jazz and classical music, but don’t ignore it because there are useful ways to apply it, even in rock and roll!

    Recap

    So using the information in this lesson, we have learned that the chord scale in the key of C, using seventh chords, is:

    I chord II chord III chord IV chord V chord VI chord VII chord
    Cmaj7 Dm7 Em7 Fmaj7 G7 Am7 Bm7b5

    And if we want to extend this knowledge generally to all major scales, we can say:

    I chord II chord III chord IV chord V chord VI chord VII chord
    maj7 m7 m7 maj7 7 (dominant 7) m7 m7b5

    So as an example, let’s figure out the chord scale in the key of E.  I’ll save you the trouble of looking at the table of major scales, and just tell you that an E major scale is:

    E  F#  G#  A  B  C#  D#  E

    Plugging in the information from this lesson, we would say that the chord scale in the key of E would be:

    I chord II chord III chord IV chord V chord VI chord VII chord
    Emaj7 F#m7 G#m7 Amaj7 B7 C#m7 D#m7b5

     

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