What if I walked up to you at your piano one day… and told you to play in the key of A, and to make sure you use a VI, V, IV, I progression on the bridge. Would you (a) freak out because you don’t know what I’m talking about, (b) make something up and hope I wouldn’t notice the difference, (c) calmly play along because you’ve already learned this stuff, and you know that what I’m talking about is just basic music theory, piano scales and keys.

Or maybe you call the police because there’s a stranger in your house. Fair enough.😂

The point is, do you know how to handle piano scales and keys in real life? Because in my experience, a whole lot of former piano students actually freeze up or try to fake their way through when it comes to piano scales and keys. (Confession, I used to be one of them!)

The Key of the Song

You may or may not know this, but every song you’ve ever heard is in a “key.” Have you ever heard someone talk about what key a song is in?

For any song, knowing the key of the song will tell us three important pieces of information:

  • What 7 notes are best for that song (this is also called a “scale”)
  • What chords are most likely to be in that song
  • “Home” aka the chord that naturally makes the most sense to return to at the end of the song (and maybe even within each song section)

That’s what people who do know piano scales and understand the keys of songs are talking about when they mention that:

  • “Imagine” by John Lennon is in the key of C
  • “Bohemian Rhapsody” by Queen is in the key of B♭m
  • “Wonderwall” by Oasis is in the key of F#m

The examples don’t really matter: if you understand the concept then you could do this for any song. The important thing is to learn how to use this information to your advantage when you’re actually playing. 🙂

How to Find the Key of (Almost) Any Song?

It’s really almost too easy to find the key of a song. In nearly every song you can think of the first and last chord (usually the “home” chord – more about that later) names the key.

So if a song starts with a C-major chord, check the ending. Does it also end on a C-major? Awesome. The key of this song is… you guessed it, C-major!

A song that starts and ends on D-minor is in the key of D-minor. Songs that start and end with A# are in the key of A#. If it starts with a dog barking and ends with a dog barking… maybe you should check on your dog. Or buy her some earplugs. 😛

If you’re still not sure, take a look at the other chords in the song. Working your way backward, you can figure out what notes are in the scale for that song. That will also tell you what key it’s in for sure. (Note: Most of the time you will not need to do this step.)

If the beginning and end chords don’t match, or you’re still not sure, you can also find the key of the song by looking at the other chords in the song, figuring out what notes are in them, and working your way backward to find the piano scale. But that’s usually not necessary, so let’s move on.

From Key to Piano Scales

Like I said, knowing the key of a song helps you figure out what seven notes are best for that song. Think about it: the more you limit the number of notes for a song, the more you can be sure which notes you should play. So while there are exceptions, and room to branch out creatively, narrowing down what to play is going to benefit you so much – especially as you just start to work on a new song.

To make this easier, you’ll never have to memorize which seven notes belong in which song, because those seven notes – the scale – are derived from a formula. If you know the formula, you can find the piano scales you need, every time.

Major Scales

Songs in major keys use a major scale formula, which is: 2-2-1-2-2-2-1.

To use this formula, start at the note named after the key of the song. So if “Imagine” is in the key of C, you can find the scale of “Imagine” starting at a C note. Then count forward according to the 2-2-1-2-2-2-1 formula.

  1. Go to the note that is 2 to the right of C (D).
  2. Go to the note that is 2 to the right of D (E).
  3. Go to the note that is 1 to the right of E (F).
  4. Go to the note that is 2 to the right of F (G).
  5. Go to the note that is 2 to the right of G (A).
  6. Go to the note that is 2 to the right of A (B).
  7. Go to the note that is 1 to the right of B, taking you back to C.

You now know that each of these seven notes is from the major scale of C: C, D, E, F, G, A, B, and C. 

This works for any major key, so go ahead and try this at home. You’ll soon see that certain notes are more common in numerous scales than others. Some scales also have more black notes than others. Remember, you don’t have to memorize the notes in any scale. Just learn the formula so you can find those notes as needed.

Finding Chords in Major Keys

Not only can you use the key of a song to find its piano scale, we can use that same scale to figure out what chords are in that key! We start by assigning a number to each note in the scale.

Let’s take this a step further. So far you’ve learned how to find a piano scale if you know the key of a song. What about if you need to know the chords in that key?

Going back to our example of “Imagine”, take a look at the key of C major. The major scale formula says that the notes in the C major scale are: C, D, E, F, G, A, B. 

Okay. What if we numbered those notes from 1 to 7?

  • Numbers 1, 4, and 5 from the scale (in this example C, F, and G) are the major chords that could work in the song. 
  • Numbers 2, 3, and 6 from the scale (in this example D, E, and A) are the minor chords that could work in the song. 

That means in any major key, there are three possible major chords and three possible minor chords!

Make sure you test this out on your keyboard or piano! Hearing that C, F, G, Dm, Em, and Am sound good together will make this more real to you. We found those chords simply by using the key of C and its corresponding scale, and lo and behold: they sound like they belong.

The 4-Chord Song Example

Have you heard of the 4-chord song? It’s pretty famous these days, but check it out here if you haven’t already.

Students of mine are familiar with a little something called the 4-chord song. It’s internet-famous for showing just how many songs share the exact same chord progression. 

All this song is, is really just a 1, 5, 6, 4 progression played in any key. I usually teach it in the key of C, but literally any key will work. So your options are wide open with this progression, and thousands of musicians and artists have taken full advantage of that fact.

For practice’s sake, let’s try it in the key of A-major. Start with the key of A and use the 2-2-1-2-2-2-1 formula.

That will give you these notes in the A-major piano scale: A, B, C#, D, E, F#, G. The next step is to assign each of those notes a number from 1 to 7. In other words:

  • Chords 1, 4, and 5 are A, D, and E.
  • Chords 2, 3, and 6 are Bm, C#m, and F#m.

You now know enough to play the four-chord progression in the key of A-major! Chords 1, 5, 6, 4 are A, E, F#m, and D.

From Key to Piano Scales to Chord Progression

Before I learned how to use all this information, I couldn’t really interact with other musicians about the key of a song or understand what they meant if they said things like:

  • “Did you go back to the 1 there?”
  • “Play a 5 there and then a 6.”
  • “Did you go to a 2 there?”

Honestly, I pretty much had to wing it and follow along as best I could! So when I say that piano scales and keys are game-changers once you understand them, I know this from personal experience!

What About Home Chords?

Not only does the key of the song tell you the seven notes in the scale and the chords that work within the song, it shows you the chord to start and end the song. As I mentioned earlier, that’s called the “home chord.”

Home chord feel kind of like coming home when you play them, because they are directly connected to whatever key the song is in. It’s usually a comforting feeling coming home, right? Especially if you’ve been gone for a while. That’s how it is when you play a progression with other chords and then home chord: it just feels right.

This all might sound a bit mysterious, but make sure you watch the video for my example. Even people who aren’t musically inclined can usually hear the difference!

Wrapping Up

This brings us halfway through my series of Music Theory 101 videos! We’ve covered a lot of ground as simply as possible.

What’s next?

In the next five videos, I’ll be answering some common music theory questions – not limited to just piano scales and keys. I’ll also be debunking some common music myths. I hope you stick around! But in the meantime, make sure you check out my free 5-day workbook if you haven’t already. Especially if you’re interested in that 4-chord song we talked about earlier, that’s covered in Day 5. 😉