Joe Satriani's Guide to Building Chords from “Stacked” Fourths

If someone had mentioned the term “stacked fourths” to me years ago, I would have had no idea what they were talking about.

But I later learned that it is really quite simple and represents a cool approach to constructing chords. In this lesson, I’d like to show you some interesting things you can do with stacked fourths. In music theory, every note in a chord can be assigned an intervallic number. Typically, we’re dealing with scales built from five to eight notes, and each note is given a number to represent its placement within the given scale.

For example, the notes B, E and G# create the sound of an E major chord when played over an E bass note, as shown in bar 1 of FIGURE 1. Now, if I change the bass note to C, as in bar 2, a very different chord results: Cmaj7#5. Building chords that will stay within the specific key—remaining diatonic to it—is just a matter of picking the notes from that key’s scale or mode and only using them as chord tones.

This is the manner by which a harmonized scale can be built, as shown in FIGURE 2, wherein I use only notes from the E major scale (E F# G# A B C# D#) to form a series of chords that are constructed using stacks of thirds, fourths and fifths. One can alternatively build, or voice, chords from notes that are all four scale degrees apart from one another, what are known as fourths. Let’s look at an example. In FIGURE 3, the first chord is built from the notes E, A, D and G, yielding Em7add4. In this case, each note is a perfect fourth above the one below it,