Seventh chords on degrees other than V
Major and minor seventh chords
Thus far, we have seen that a dominant seventh type chord can built on the fifth degree of the scale, creating a unique chord that has a major triad with a minor seventh above. In C, the chord is G B D F.
Seventh chords can be built on any step of the major scale. Notice that when we do so, only the chord built on V is of the dominant seventh type, comprised of a major triad and the minor seventh interval. The others fall into three additional categories: major seventh chords, minor seventh chords and two types of diminished seventh chords.
Let's take the major seventh and minor sevenths first.
If we look at these seventh chords, based on the scale degrees, we can notice three things:
- The naturally occuring minor triads, based on the vi, ii and iii degrees of the scale, all are turned into the minor seventh chords the the addition of the minor seventh above the root.
- The other naturally occuring major triads, the I and IV, are all turned into major seventh chords with the addition of a major seventh above the root.
Note the two ways in which these are labeled. Using pure Roman numeral notation, these chords are simply labelled with the root of the chord, followed by the 7. However, in popular chord notation, it's very important that these chords be labelled with the "min" for minor seventh and the "maj" for major seventh. In popular chord notation, the simply 7 by itself means the dominant seventh type. Thus G7 is the G dominant seventh chord, C7 is the V7 of IV, D7 is the V7 of V and so on.
In the classical harmony of the eras of Bach, Beethoven and early Romanticism, these seventh chords were rare, and if they did appear, the seventh was always prepared in a previous voice. (We study this in detail during the second semester). In the later part of the 19th century and especially io 20th Century Impressionism (Debussy and Ravel), the seventh chord increasingly became an accepted sonority an any step of the scale. This impressionistic harmony led directly into the types of rich chordal harmony that we are used to hearing in the fields of jazz, popular commercial music and jazz-influenced Rock.
Here for example is a jazz standard, notated as a lead sheet for improvisation. The chord designations signal to the guitar and/or keyboard player to voice chords as various types of minor sevenths, major sevenths and dominant sevenths. Note again: the appearance of the bare "7" always refers to a dominant-seventh type chord. The other sevenths, the majors and the minors, are clearly spelled out.
<A STANDARD WILL APPEAR HERE>
The Diminished Triad and the Diminished Seventh Chords
There remains one type of seventh chord to discuss—that of the diminished seventh chord. If you glance at the seventh chords in the graphic at the top of this page, you'll notice that we have not yet discussed the seventh chord that occurs on the seventh step of the scale. Indeed, we have barely discussed even the triad based on the seventh degree. That is because the vii triad is a diminished triad, lacking the solid perfect fifth that all the other primary and secondary triads possess. This makes all chords based on the seventh step of the scale a special case, one best discussed all together.
The Diminished Triad
I have scrupulously avoided discussion of the diminished triad until now, because this triad is best understood as a dominant seventh chord without the root. This is because the diminished triad contains that same tritone as the dominnat seventh chord, and it functions exactly the same way: its notes resolve to the root and third of the tonic triad. Notice that in Roman numeral notation, the vii triad is always given a little "degree" sign as a superscript, which signals that the triad is diminished (i.e., without a perfect fifth).
Thus it is always best to view a diminished triad as "dominant seventh chord without the root." In classical harmony, this triad appears often as a substitute for V7, and it most often resolves in the usual way, that is—up a step to the tonic chord. Diminished triads by themselves are a little thin sounding; thus they more often occur, both in classical and in popular and jazz harmony, as fully diminished seventh chords.
The Diminished Seventh Chord
The Fully Dimished Seventh Chord (or just "diminished seventh chord") is created by adding another minor third on top of the diminished triad. Since the diminished triad is, itself, a stack of two minor thirds, this diminished seventh chord becomes a uniquely symmetrical sonority: it is comprised of three minor thirds, stacked on top of one another. You will also notice that this sonority creates two tritones, interleaved one with the other.
The resolution of this chord points even more strongly toward the tonic triad, in this case in the key of C. The B-F tritone resolves inwards to C and E, as before. The Ab-D tritone also pull inwards, towards the E and the G. It is the strength of this harmonic pull that gives the chord its unique sound and function within tonal music.
Listen to the last two examples to hear the sound and the pull of the tritones of the diminished seventh chord.
The diminished seventh chord is an essential harmony in Classical music, from Bach through to late Romanticism. In popular music, it is used much more rarely; in generally, this chord appears with its root intact (that is, the G). Thus in general, in popular music, jazz and jazz-influenced rock, the diminished seventh chord will appear along with the its root (played by the bass player), creating a full dominant flat nine chord. Notice the relationship between the V7, the vii diminished seven and the fully dominant flat nine. The Ab in this case is considered to be a ninth above the root of the G triad, and since it is an Ab, becomes a "flat nine chord" (wriiten in standard Roman numeral notation as "V7-9.")
The Half-Diminished Seventh Chord
There remains one final seventh, the so-called half-diminished seventh chord. In jazz harmony, this same chord is known as the "minor-seventh flat-five" chord, which better explains its configuration. In A minor, it appears as the ii7 chord.
To understand this better, it is necessary to explore a little more about major and minor harmony. For this, a new page is needed.
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