Most of us know the definition of a sus chord: it is a dominant chord whose major third is replaced by the perfect fourth a half step higher.
But I encounter lots of musicians who know this definition and can’t seem to make heads or tails of it in practice. Perhaps this post will shed some helpful light.
Look at a very simple ii-V-I cadence in the key of C:
(Note that the G7 voicing here is in fact a G9. For those of you new to jazz, it’s a common practice to add upper chord tones to voicings, and to omit the fifth, for the sake of voice leading and overall sound.)
Listening to the chords, the sound of the D7 conveys a stable, consonant soothing sound, whereas the G7 conveys more of a “voyage underway”—a tension that will likely resolve to the C before long.
The transition between the D7 and the G7 amounts to exactly two things: (1) the root moves and (2) the seventh of the D7 resolves down a half step to the third of the G7:
We can divide this transition into a two step process, where first the root movement occurs, then the half step resolution:
As we see, the intermediate step is a sus chord. This gives us a useful way to view sus chords:
A sus chord is midway between the iim7 chord and the V7 chord of a ii-V.
It has the consonant, soothing quality of the ii chord which, unlike the V7, contains perfect fifths (between the root & fifth and the third & seventh) and no tritones (the major third and minor seventh of a dominant chord form a tritone). But it takes on some of the sense of movement that a dominant chord conveys. If a dominant chord feels like a voyage underway, then perhaps a sus chord feels like it is preparing to embark on a voyage. It is no coincidence that the composition in jazz that is most closely associated with sus chords is entitled “Maiden Voyage“!A sus chord is midway between the ii and the V of a ii-V-I progression. Click To Tweet
A state of “suspension”
“Sus” stands for “suspended.” In Classical theory, a suspension refers specifically to the fourth—or occasionally the second—that is held over briefly from the previous chord. In classical music and in the Tin Pan Alley jazz standards, sus chords are almost always resolved quickly.
But in modern jazz, suspended cords can last indefinitely without resolution—as is the case in “Maiden Voyage“. In such cases, the sus chord conveys a broader sense of “suspension”… almost like a feeling of suspension of gravity or suspension of time… as though harmonic forces continue to be steadily at work, but they are not resulting in any change. Once again, the nautical metaphor seems perfect: when you’re out on the ocean, you may know that you are moving forward, and still you may have no sense of forward progress at all, judging by your proximity to the landmarks you see.
A sus chord is a “two chord” over the root of its corresponding “five chord”.
That is to say, D7/G = G7sus. Any voicing for a minor seventh chord is a voicing for a sus chord a perfect fifth lower. In fact, whether a band plays a D7 or a G7sus is entirely up to one musician: the bass player. Anything anyone else plays is the same either way. That gives us a simple answer for how to improvise over a sus chord:
Improvise over a sus chord exactly how you would over a minor seventh chord a fourth lower.
We can see that, case by case, any scale choice for D7 is a great scale choice for G7sus:
|Scale||Dm version||Relative to G|
|7-note scale||D Dorian||G Mixolydian|
|Pentatonic||D minor pentatonic
(D, F, G, A, C)
|G “sus pentatonic”
(G, A, C, D, F)
(see Weiskopf or
|F and G triads
(built on minor 3 & fourth)
|F and G traids
(built on minor 7 & root)
Observe also that the chord tones of D11 (1, 3, 5, 7, 9, 11) are in fact the 5, 7, 9, 4, 13 and root of G13sus, respectively. Not only do the proper scales coincide between D7 and G7sus but, in fact, the important notes do as well—so if you emphasize the chord tones of a D7, the results sound great over G7sus. Accordingly, any bebop line you might play that targets chord tones of D7 (or D9 or D11) will sound great over G7sus (or G9sus or G13sus). For example:
Listen to the line over D9:
And now listen to the same line over G13sus:
Flattening the Ninth
What can we say about the sus9 chord, the darker version of the sus chord? Just as we viewed the Gsus chord as midway between the two and the five chord in a ii-V progression, we can view the G79sus as midway between the two chord and the five chord in a minor ii-V progression:
Playing the third over a sus chord
We’ve all learned at some point that over normal dominant chords, the fourth is an “avoid note”—meaning that it’s fine to use it as a passing note, but we’d better not sit on for any appreciable duration. For example, it doesn’t work to use the 11 in a dominant voicing:
However, we absolutely CAN use the third in a sus voicing. It’s a beautiful sound, akin to the D7(add 6) but over a G root: D7(add 6)/G = G7sus(add 3):
Accordingly, the major third is not an avoid note over sus chords. We can use it to great effect in our improvisations.
This post has a sequel entitled “Sus Chords Part II: Their Uses.”