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1 Seventh and Added-Sixth Chords: Overview We first learned about seventh chords as a 4-note tertian harmony, or a triad with a interval added. We also spent a fair amount of time on dominant seventh chords as we worked on our part-writing. We have also mentioned that there are other types of seventh chords, and you may already know some of these. 7th So now it’s time to ask just how many types of seventh chords there are, and how to spell and label them. If we agree that seventh chords are simply triads with an added 7th, then that gives us eight possible ingredients to work with: the four types of triads, and the four 7th intervals shown in Figure 1. Figure 1: Triads and Sevenths The augmented 7th is not useful, because it is enharmonic to the perfect octave. Further, the diminished 7th interval is often enharmonically spelled as a major 6th. When this happens, the chord that results is called an added-sixth chord. Combining the four triad types with the major seventh, the minor seventh, and the diminished 7th/major 6th gives us 12 possible chords. Here are the possibilities in the key of C, with their popular symbols: Figure 2: Twelve Possible Seventh and Added-Sixth Chords Some of these are very common; others (like the diminished-major 7th) are rarely used. The one chord that is almost never used is the augmented triad with a major 6th, which sounds like an inverted minor/major 7th and has no tonal function. Added-Sixth Chords Adding a major 6th onto a triad adds some color without adding a “true” 7th, which creates a tendency tone. Added-sixth chords were rather common in late 19th-century music, including a lot of American standard tunes that formed the basis of the jazz © 2013 TMRW Music 2 repertoire. Not everyone considers added-sixth chords to be a type of seventh chords, but I like including them here because they are quite common, and I haven’t heard any better way to explain them! Another aspect of added-sixth chords is that they can be seen as inversions of other seventh chords, as shown in Figure 3. Figure 3: Added-Sixth Chords as Inverted Seventh Chords Added-sixth chords can also occur when a chromatically-moving line is placed against a tonic triad. This creates slight color variations in a chord that is not really going anywhere. Jazz musicians call this technique CESH, for Chromatic Elaboration of Static Harmony. This technique is common in many styles including classical, jazz, and rock. Figure 4: Chromatic Elaboration of Static Harmony (CESH) Seventh Chords in Key Context The major, natural minor, harmonic minor, and (ascending) melodic minor scales each produce their own particular set of diatonic seventh chords. Note the subtle differences between the popular chord symbols and the traditional Roman numeral analysis: © 2013 TMRW Music 3 Figure 5: Seventh Chords from the Major Scale Figure 6: Seventh Chords from the Natural Minor Scale Figure 7: Seventh Chords from the Harmonic Minor Scale Figure 8: Seventh Chords from the Melodic Minor Scale We typically divide these chords into categories based on how commonly they are used in traditional music: dominant sevenths (V7), leading-tone sevenths (viiø7 and viio7) and non-dominant sevenths (everything else). Over the next few chapters we will look at usage and part-writing concerns for each of these types of chords. There is one other seventh chord type that we did not cover here—seventh chords with a lowered fifth, or “flat-five” chords. These chords do not arise from the triadic system and will be dealt with later in a discussion of altered dominant chords. The chart on the next page provides a summary of all of the seventh and added-sixth chords, along with their most commonlyused popular chord symbols. © 2013 TMRW Music 4 Figure 9: Chart of Seventh and Added-Sixth Chords Triad Major Major Major Minor Minor Minor Augmented Augmented Augmented Diminished Diminished Diminished Major (♭5) Seventh M7 m7 M6 M7 m7 M6 M7 m7 M6 M7 m7 d7 m7 Popular Name Major 7th Dominant 7th Major 6th, added-6th Minor-major 7th Minor 7th Minor 6th Augmented-major 7th Augmented dominant (not used) Diminished-major 7th Half-diminished 7th (“Fully”) Diminished 7th Dominant flat-five Symbols M7, maj7, ∆7 7 6, M6, add6 m(maj7), m(∆7) m7, mi7, –7 m6, mi6, –6 + (maj7), + (∆7), maj7(#5) + 7, 7(#5) o(maj7), o(∆7) ø7, m7(♭5) o7 7(♭5) © 2013 TMRW Music