How do I tell which power chords go with a key?

Question

I'm just barely getting my feet wet with some of the theory behind composing in a certain key and found the standard way to find the seven chords that correspond to a major scale. You take the root note, apply T T S T T T S to get your seven scale notes, then apply Maj Min Min Maj Maj Min Dim to get your seven chords. I've done this a few times and it works. You play the chords and weedle around on the scale and you get something serviceable.

What I can't figure out is how to incorporate power chords into the scale. For example, if I want to play power chords around a G Major scale, how do I calculate which cords will naturally sound good?

Answer 1

Power chords omit the third, using only the root and perfect fifth of the chord. You can substitute them for any chord with a perfect fifth, major or minor. You cannot, however, substitute a diminished chord or augmented chord with a perfect fifth.

Therefore, in a major key, you can play power chords over anything except the diminished vii chord (B diminished in C major, D♯ diminished in E major, G♯ diminished in A major).

Answer 2

The simple answer is this; to technically answer you question, every power chord is in a diatonic scale except the one where the scale has a flat 5 (so F# in the key of G major)

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The real answer is that that answer is completely useless. Why?

• There are plenty of situations where chords outside of this set also work Bb and F power chords are both pretty common in rock songs in G major for example.
• In order to know which chords you want to use, you need to have an idea of how each chord behaves, what it can lead to, how it functions in a song etc. If you pick random power chords from the scale (say, |D|E|C|F|A|) it'll probably sound like exactly that, random chords.

That is to say, sometimes chords that are "in a scale" sound bad, and sometimes chords outside of the scale sound great.

Now, maybe your next question would be, "if the major scale is useless in telling me what power chords to use to write a song, what should I use?" The problem is that any list of "rules" of what power chords work well in rock music is pretty much asking "what is the harmonic structure of power chord based music (grunge and punk rock etc.)". That's an interesting question for sure, but requires a very long answer.

It might seem like I'm being obtuse, and or lecturing rather than answering your question, but if you start trying to build rock music from power chords based on the major scale, that's probably worse than basing it on no theory at all. The modern problem of the internet musician is that they often jump straight into "scales" thinking that will teach them how to write music or play solos, when they would learn a whole lot more from the old fashioned way of actually studying pieces of music.

I hope you don't consider this too off-topic from your question, but these are your options:

• Find some books, blogs etc. that go into detailed theoretical analysis about harmony in rock music.
• Listen to, and learn a whole bunch of songs, and try and notice what's going on, what chords get used and when, and why.
• Write "by ear": play what sounds good to you, try and learn from your own intuition.

All to often aspiring songwriters seem to rank them in that order, when in reality, the musical journey goes exactly the other way round. Hell, I personally love reading about and discussing theory, and always advocate it; but there are plenty of amazing songwriters using just their ears and knowledge of other music. There isn't a single one who learn a couple of scales and tried to piece them together in songs, and didn't bother with the other 2 steps though.

Answer 3

The term 'power chord' is a misnomer. It is an egregious piece of branding for 'chord with only two notes so it's easier to play and rarely sounds wrong'. After all, how can it have more 'power' than a six note guitar chord? That said, there is a purity to the sound of notes a perfect fifth apart. Nomenclature aside, if you take one extra step you can come up with two note chord (diad) for 'all occasions'. Bring the higher note of your power chord down one fret for a diminished sound. Bring the higher note up one fret for an augmented sound.