How To Form 7th Chords

7th Chords are perhaps the single most confusing area of music theory for musicians to master. They are not difficult, but their construction is often explained in such a cryptic way that even the simplest concepts are made difficult.  This set of articles will attempt to explain 7th chords in a clear, but thorough, way.  Make no mistake, 7th chords do take some effort to understand, but are otherwise within the grasp of most pianists.

All 7th chords are formed as a combination of of four notes (i.e., a basic triad, accompanied by a fourth note, the interval of a 7th above the root). To aid our understanding of 7th chords, we will use a chart, much as we did in understanding simple chords. There are six basic types of 7th chords, all of which we will cover: Major, Dominant, Minor, Half-Diminished, Diminished, and Augmented.

In order to find the notes of the 7th chords, we will define them in terms of a Triad and an Interval. The Triad will be either a Major, Minor, Diminished, or Augmented chord, based on the root. The Interval refers to the 7th which we will add to the Triad. It is called a 7th because it is located the interval of a 7th (either Major, Minor, or Diminished) above the root of the chord. We will now see how the triad and the interval work together to form a 7th chord.