Sevenths

In a scale or chord, a seventh is the seventh note up from the root. Looking at an A-major scale, the seventh is G#. From A to G# is a major seventh, or an interval of five-and-a-half steps (11 frets). A minor seventh is one half step smaller than a major seventh, or an interval of five whole steps (ten frets). For example, a minor seventh up from A is Gn. As a shortcut when dealing with chords, you might try thinking of the major seventh as just a half step (or one fret) below the root and the minor seventh as a whole step (or two frets) below the root.

The various kinds of seventh chords you may have seen are just triads with an interval of a seventh up from the root added on. The question is, what kind of seventh–major or minor–is being added to what kind of triad: major, minor, augmented, or diminished?

To keep things relatively simple, let’s leave the augmented and diminished triads out of it for now and stick to just major and minor triads and sevenths. You’ve got four possibilities: major triad with major seventh, major triad with minor seventh, minor triad with major seventh, and minor triad with minor seventh. If that makes your head spin, try thinking of it in a little grid like this:

There’s a different name for the result of each one of these combinations. Two of them are pretty logical. If you add a major seventh to a major triad, the result is called a major-seventh chord. Similarly, if you add a minor seventh to a minor triad, the result is called a minor-seventh chord. These are usually abbreviated maj7 and m7 (or min7). So when you see Amaj7, you can think to yourself, "Aha! Everything major–an A major triad with a major seventh on top." Since the seventh note of an A-major scale is G#, what you need is an A-major chord with a G# buried in the middle or perched on top. In other words, one of these two examples:

A-major-seventh chords

Likewise, when you see Am7, you can unpack it by thinking, "OK, everything’s minor . . . an A-minor triad with a G natural added in." (G natural is a half step lower than the major seventh, G#, and therefore is the minor seventh of A.) Either one of the chords below would fit the bill nicely, with a G natural either insinuated into the midst of the chord or waving around conspicuously on the high end.

A-minor-seventh chords

So far, so good. But now, alas, is where things get a little peculiar. What do you call a major triad with a minor seventh on top? Not a major-seventh chord, because the seventh itself is minor. And not a minor-seventh chord, because the triad itself is major. This hybrid of major and minor is called a dominant-seventh chord. Confusion can ensue quickly, because a dominant-seventh chord is generally referred to as simply a seventh chord: an A dominant-seventh chord, for example, is simply written A7, not Adom7. So you need to know a couple of things: when you see A7, it means A dominant seventh, and that in turn means an A-major triad with a minor seventh added, or an A-major chord plus a Gn, which would look like one of the two chords below:

The last possibility, a minor triad with a major seventh, is pretty rare, so we won’t worry about it too much. It’s also notated the most literally: an A-minor triad with a G#, or major seventh, added is written Am(maj7). Imagine that.

Going back to our diagram, then, we can fill it in like this: