Power Chord Theory

Music Theory Major Scale Theory & Key Signatures
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Are they electric or really strong? They're our friends who can rock and they're not Major or Minor players!


View the full lesson at Power Chord Theory | JustinGuitar

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Perfect 4ths also sound pretty good with distortion. Pretty sure it’s the way distortion replicates frequency intervals across the spectrum. Could probably sort it out in a day or two with some fourier analysis.

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Funnily enough, a 3 string powerchord contains that interval.

If you take a C powerchord you have C to G (the fifth) and G to C (the fourth). Played together the G and C are actually an inverted C5 chord used in many songs such as Smoke on the Water.

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You have hit upon a connection between all interval types there @dave.pritchard101

An inverted 5th = a 4th (and vice versa).

An inverted 3rd = a 6th (and vice versa).

Can you see you simple mathematical sum that would allow you to know the inversion for any interval?

Cheers :blush:
| Richard_close2u | JustinGuitar Official Guide & Moderator

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I didn’t think of it as an inversion makes sense though.

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A 5th plays well because its wave frequency is 3:2 of the fundamental. This is the “nicest” ratio after 2:1 (an octave), and it means that the wave of the fundamental and of the 5th constructively interfere after only 2 wavelengths of the root (or 3 wavelenght of the 5th)

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There are some folk in the community who understand and appreciate the fundamental physics of wave motion. Thanks for the extra info @Armi

Cheers :smiley:
| Richard_close2u | Community Moderator, Official Guide, JustinGuitar Approved Teacher

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I have enough to worry about playing power chords never mind the theory behind them!

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@Richard_close2u You’re welcome! I love the fundamental aspects of music because this is the reason why, as well as math, this language is universal and the same concepts were achieved independently throughout history

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In the notes of this lesson it says “While a Major Chord has a root, a major third, and a fifth, a Power Chord consists of only two notes” which I’m guessing is not quite correct based on this lesson https://www.justinguitar.com/guitar-lessons/power-chords-bg-1201 which shows chords with three notes.

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Hi Stuart,

Happy new year :slight_smile: It actually is correct as the root (or any other note) and its octave(s) are not counted separately. For example, the E5 power chord includes the notes E (root) and B (fifth). There are several ways you can play it, starting from the basic power chord grip with the root note on the 6th string to more elaborate ones like 079900.

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Happy New Year to you.

Thanks. Just watched the next video in the series which explains this.

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Here’s another use of Mr. Cato’s Nifty Key Diagram.

Use whatever memonic you like to come up with the diagram.

Then look :eyeglasses:

Pick any note and call it the root, then the adjacent note on the right it it’s 5th. So if you have a memonic for FCGDAEB, Bob’s your uncle. You have the key to power chord construction.

Mr_Cato_Slick_Trick
Mr_Cato_Slick_Trick1896Ă—300 12.7 KB

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Why thirds may sound worse:
12-tone equal-temperament is kind of bad at approximating the fractions of a perfect third (but is quite good for fourths and fifths).
If you think of a chord being “powerful” when it’s a simple ratio of frequencies, it might explain your feeling.

There’s a cool graphic in the following article: 12 equal temperament - Wikipedia

For someone interested in the mathematics behind it, this could stop me playing guitar for days :slight_smile:

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The Circle of Fifths does exactly this also (and more). :slight_smile: The Circle of Fifths - where does it come from, where does it go?