The Myth of the Evil Fourth

I’ve been playing guitar for quite some time, but I only started singing about two years ago when I was offered a weekly gig directing a choir.

As I practiced and struggled and practiced more, I noticed a strange trend: Whenever I tried to sing a major scale, the fourth degree always came out sharp. All of the other notes were fine. What’s your problem, fourth?

Could this have something to do with the fact that every explanation of modes I read as a young lickster contained some doomsday prophecy warning about the fourth degree of the scale? I remember reading about the evil fourth in nearly every explanation of modes and scales I sought out. Better to use the sharp fourth! The natural fourth is dissonant! they all shouted. If a bunch of people say it, it must be true, right?

This made absolutely no sense to me. First of all, natural fourths never sounded weird whenever I tried to hear what was so bad about them. I’d play a C chord, then play the fourth degree, F, and be struck by how un-wrong it sounded. What confused me even more was that a lot of people seemed to insist that the fourth degree was not only unfavorable but actually dissonant. Why would someone consider the fourth dissonant, I thought, when a major seventh is totally fine?

Eight years and a music degree later, I started to understand what all of this fourthism was about. I’m going to share what I’ve come to, and I hope it helps you in your melodic journey.

Saying that “fourths over certain chords are dissonant” isn’t really accurate. It’s not that they’re dissonant; it’s that they can confuse the essential parts of the harmony of a given chord, leading to unwanted ambiguity, not tension. Check it out: The most important notes of a chord – the “harmonic DNA” – are the third and seventh. These two notes create either a fourth or a sharp fourth. In other words, a C major 7 chord is made with the notes C, E, G and B. The E and B are the most important notes of this chord. G dominant 7 is made with the notes G, B, D and F. The B and F are the most important notes of this chord. So if the chord is Cmaj7 and you hang out on the note F in the melody for a while, the chord will start to wonder if it’s Cmaj7 or G dominant 7 because the F you’re playing and the B already happening in the chord will create the harmonic foundation of a G dominant 7 chord.

Here’s a different way to look at it: The natural fourth compromises the resolution to the tonic chord, which is usually the most important and musical part of a melody or solo. In most musical structures, a key’s dominant chord sets your ear up for the tonic chord. If the natural fourth is played over a dominant chord, your ear thinks the chord has resolved even though it hasn’t because this note is the root of the chord that will happen in a moment. If the progression is G7 – Cmaj7, playing the fourth of G7 over G7 (C) tells your ear that the Cmaj7 has already happened. When the Cmaj7 finally does come around, it feels awkward and lacks momentum.

Some things to remember:

Music happens horizontally, not vertically. In an improvisational context, just about every “rule” can be bent and broken, including the one I’ve just outlined. Trust your ears. They know more than you think.

Be suspicious of the idea that you can study a certain aspect of music, extract a formula or equation from it, then apply it whenever you’re making music.

If this makes no sense to you, great! Figure out why it doesn’t. Then you will have learned something.

-Al Teodosio,