How To Figure Out The Key Of A Song

How To Figure Out The Key Of A Song (Plus: A Chart With All The Chords In Each Key)

If you’re already signed up for our Klassik tribe membership, you’ll be getting this and free training every year.


But I thought it’d be helpful for those of you going it alone to have this information at your fingertips too.


What Key Is This?

If you’ve been following along in #KlassikTips you’ve learned

  • to ID notes on your fretboard by their actual names,

  • which notes go into which keys,

  • how to build simple & fancy chords,

  • which chords belong in each key, and

  • what the “function” of each of those chords is.

But how do you know how to figure out the key of a song in the first place?

Here’s a list of questions that will help you decide.


Although putting this in a checklist makes it seem really formal, this is something that will eventually happen automatically, in a matter of seconds.


I trained my brain to do this, and you can too.


With a little practice, you’ll be able to take a snap “reading” of a song (or a section of a song).

  1. Is there a chart with a key signature?

  2. Did someone call a key?

  3. What’s the last chord in the song?

  4. Is there a clear dominant chord?

  5. Is there another clear chordal movement that’s a key giveaway?

  6. Are all the chords diatonic to a certain key?

  7. Are most of the chords diatonic to a key, with some non-diatonic (but not entirely unexpected) chords sprinkled in?

  8. Can this be written in more than one key?

  9. Is one easier than the other?

  10. Does it even make sense to think of this as being in one key?

I’m going to explain each of these in order, but I want to begin by saying that you should be going through this checklist in this order when trying to determine a song’s key.


This is going to be helpful to have a chart with all the chords in each key open in a separate window.


Is there a chart with a key signature?

Probably the easiest way to determine what key you’re in is when the written music tells you the key.


Although we didn’t dwell on it in the Circle of Fifths course, you already have this knowledge because (assuming you did Circle), you already know how many sharps or flats go in any given key.









On a chart written by a literate musician, there will be key signature––some number of sharps or flats between the clef and the time signature:

In this example, one flat means that the song is in F.

So when you see this at the top of a chart:

You’ll know that it’s in the key of E.

And when you see this:


You’ll know it’s in D.

Don’t worry about that whole 4/4 – 6/8 – ¢ “time signature” thing for now––the next GuitarOS course is going to teach you all about rhythms.


Did someone call a key?

Of course, if someone says, “this is a blues in G” or “we’re playing Dock of the Bay, but in F,” you’ll obviously know what to do.


What’s the last chord in the song?

If you’re learning a song from a recording or reading a chart written by a less-than-literate musician, you can look to the last chord of the song––it’s frequently the I chord.

It’s not a hard and fast rule though. If the song changes to a new key somewhere along the way, this won’t be of much help.


And there are plenty of songs that purposely end on a chord other than the I.

If the last chord of the song gives you the feeling of resolution, it’s probably the I.

But if the last chord feels unsettled, it probably isn’t.


Is there a clear dominant chord?

If we look at the extended chords that show up diatonically (diatonic = made up of only notes from within the key), we see that there’s only one that’s a dominant 7 chord: the V.

If you see a set of chords that only has one dominant 7 among them, there’s a pretty good chance that that chord is the V.


Is there another clear chordal movement that’s a key giveaway?

You can also be on the lookout for other mini-progressions like ii-V or IV-iv.

When I see Am-D, my brain goes straight to “ii-V in G.”

When I see F-Fm, my brain goes right to “IV-iv in C.”


Are all the chords diatonic to a certain key?

(Again, “diatonic” means only using notes from within the key––no outside notes.)

If you see this progression:

Am-Bm-Em-D


…you can see that the only key that has all of those chords diatonically is G:

So even though there’s no G chord, it’s in the key of G.


This example is from Dave Matthews Band’s #41. The band eventually does go to the G chord, but it takes them a minute and a half of this progression before they do.



Are most of the chords diatonic to a key, with some non-diatonic (but not entirely unexpected) chords sprinkled in?

Here are the chords from John Mayer’s Badge & Gun:

All of the chords except that A7 are diatonic to G:

But when we look at the commonly-occurring non-diatonic chords, we see that A7 isn’t entirely unexpected:


Can this be written in more than one key?

Is Sweet Home Alabama a I-bVII-IV in D?

Or a V-IV-I in G?

If you do a google image search for “Sweet Home Alabama sheet music,” you’ll see that roughly half of the transcriptions show it in D, and half in G.


Is one easier than the other?

My personal preference is to think of Sweet Home Alabama in G, because it’s easier that way.

But thinking of it in D is just as correct.

I have another post cued up for next week, talking all about the implications of this idea, and what it means for modes.


Does it even make sense to think of this as being in one key?

For some tunes, it doesn’t really make sense to think of them in one single key.

Here’s The Allman Brothers’ Melissa:

Although we don’t leave the key long enough to warrant writing in a key change, for measures 11 & 12 we’re very clearly playing I-ii-iii-IV in the key of A.

If you were soloing over these changes, the E major scale that sounded so good over the rest of it suddenly doesn’t fit quite right––you have to smoothly switch to A major for those two bars.


Jazz music is filled to the brim with this sort of thing––there’s ii-V-I, and then I becomes minor and it’s the ii of some other key…


Jazz musicians still use this same roman numeral language, but they’re not beholden to whatever key is written on the chart––they’re talking about what key the song is in for this subsection of the tune.


Playing fluidly over chords that change key frequently requires an equally fluid mindset about keys.


Learning to see subsections of songs as being in their own key is the logical extension of getting good at seeing songs as being in a key.


We’re going to touch on this again next week when we talk about how all of this feeds into our understanding of modes.


What About Minor Keys?

It’s worth mentioning that up until now we have studiously avoided talking about minor keys––keys where the “one chord” is minor: i.

Minor keys are their own thing, and worthy of their own article (which we’ll get into in two weeks, after our discussion of modes).


Recap

  • At the top of a well-written chart, you’ll see a clef & a time signature, and in between them is a key signature––the number of sharps or flats tell you what key the song is in.

  • If the last chord in the song gives you a sense of resolution, it’s probably the I.

  • The only diatonically occurring dominant chord is the V. If you see a dominant chord, there’s a decent chance that it’s the V.

  • Other clear chordal movement that suggest a key are ii-V and IV-iv.

  • Sometimes you’ll be able to see that all of the chords are diatonic to a certain key.

  • Even if the I isn’t one of those chords.

  • Other times most of the chords will be diatonic to a key, and the non-diatonic chords will be common enough.

  • Some songs be written in more than one key.

  • One is usually easier than the other.

  • Some songs move fluidly through different keys.

  • Getting good at quickly seeing the key of simpler songs will lead to getting good at spotting those times when a subsection of a song is in a different key.

  • a chart with all of the chords in each key can be found here

  • if you’d like to be walked through this one piece at a time, sign up for GuitarOS

See you next week, when we’ll talk about what all of this means for modes.

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