Lesson 12 - Introducing Seventh Chords
Now that we have learned a little about triads, we are now ready to look at seventh chords.If you add another note an interval of a third above the top note of the triad, you get a seventh chord. It gets its' name due to the added note being the seventh note of the scale above the root -- we call that note the seventh. You can add the seventh to any triad using both the major third and minor third intervals. There are potentially eight different types of seventh chords. However, seventh chords based on the augmented triad are rarely used. Seventh chords built on major, minor and diminished triads are very common.
In general, we identify a seventh chord based on the interval between the root and third, and the interval between the root and the seventh. We then added the term seventh at the end. For example: you can have a seventh chord identified as a Major-Minor Seventh chord. This would mean that the interval between the root and third is a major third, and the interval between the root and seventh is a minor seventh -- this is a major triad with a minor seventh, hence, major-minor seventh. (The interval between the root and fifth is understood to be a perfect fifth unless we are dealing with a diminished seventh chord -- but in that case a different naming convention is used. We will look at that a little later.)
The written version of this naming convention uses the same rules used for naming intervals -- except that we add a letter because of the added interval.
M - MajorThe seventh chord name has three parts. The first names the root-third interval, the second identifies the interval between the root and seventh. The third is simply the number 7 that identifies it as a seventh chord. The above seventh chord name would be written Mm7. If you have a seventh chord that is a minor triad with a minor seventh, it would be written mm7.
m - Minor
+ - Augmented
o - Diminished
As we alluded to earlier, there is a slightly different naming convention for seventh chords built on the diminished triad. The degree symbol (o) is still used for naming the triad and the number 7 is used for identifying it as a seventh chord. Because we will be adding a minor or major third to the top of diminished triad, the seventh interval is either going to be diminished or minor. If the former is used, it is called fully diminished because it has a diminished triad and a diminished seventh -- written o7. The latter is called half diminished because it has a diminished triad and a minor seventh -- it is written with a degree sign with a slash through it followed by the number seven (which I cannot duplicate on this webpage).
In the next three lessons we would look at the three most common seventh chords in more detail.
©2004 Keith Prater