How to find the key of a song

26.02.2022 Ben Maloney Music education

To find the key of a song using notated music, check the key signature at the left of the stave. But if you’re reading a different type of notation, or listening to a recording, then the chord that starts and ends the song will in most cases tell you the key.

Unfortunately, it’s not always that simple. Each key signature is shared by one major and one minor key, and many songs don’t even start in the key that they’re really in – let alone stay in it. 

If that quickfire guide didn’t help you to find the key of the song you’re learning, then keep reading. The following steps will tell you everything you need to know in order to figure out that key.

But first, let’s understand what a key actually is before we learn how to find it.

What is a key?

key is a group of notes that forms the framework of a piece of music. Usually, there are seven notes in this group, and they are arranged and often expressed in a scale. For instance, the notes of the key of C major are the same as those in the C-major scale.

The majority of songs in the key of C will stick more or less to these seven notes, grounding the piece in that key. The first note in each scale, called the tonic, is the most important, and that’s why the key is named after it. For the most part, songs will start in a key and stay in that same key. 

If a different note is suddenly thrown into a song in F major, such as B-natural, then it’ll sound out of place, because it isn’t in the song’s key. In many cases, especially when it comes to classical music, the key isn't as black-and-white as notes on a stave. But don’t worry too much about that for now. 

Now that we know what a key is, it’s time to think about how to find it. Here are some easy questions to ask that should help you figure things out.

Is there a key signature on sheet music?

If there’s a page of sheet music in front of you, chances are that there’s a key signature on it, and if there is, then checking what it is will be the easiest way to figure out the key. 

A key signature is an arrangement of a number of sharps (♯) or flats (♭). Positioned between the clef and the time signature at the far left of the stave, it indicates the notes that make up the key.

The key signatures above, for example, denotes either E major/C♯ minor and E♭ major/C minor. Refer to the image below to see the other signatures and the keys that they’re matched to. It depicts the circle of fifths, a method of organising signatures according to the quantity of sharps and flats.

Each key signature on the circle has either one more, or one less sharp or flat than its neighbour. Look at a keyboard and you’ll see that the tonic of each key is seven keys away from its neighbour. This gap - or interval - is known as a perfect fifth, and that’s why it’s called the circle of fifths. 

If you learn the signatures depicted, you’ll instantly be able to find the key of a written piece of music. There is a small snag, however.

As you can see, each key signature is shared by a major key and a minor key, known as relative to each other, which means that a key with three sharps in it could be either A major or its relative minor key, F♯ minor. 

To determine which of the two the key is, you’ll have to do a bit of simple analysis by looking at the notes, chords or harmonies in the music. 

If they’re centred around A-major chords, then – you guessed it – the piece is probably in A. If, on the other hand, they’re built primarily around F♯-minor chords, then the key is likely to be F♯ minor.

What if there’s no key signature - or no sheet music?

If you’re listening to a recording or working with a more casually notated piece of music, then there won’t be a signature to help you find the key of the song. If this is the case, then a little bit of analysis is in order.

The challenge is to find the tonal centre of the song, which tends to be the chord which the notes or harmonies will move around.

This chord is known as the tonic chord, and is identified by the key, so the tonic of the key of G major is the chord of G major, comprising the notes G, B and D - see below. These three notes constitute a triad, and triads are the most common and effective way of outlining a chord.

Big chords at the end of pieces of classical music often bring a satisfying sense of resolution. That’s what it is to return to the tonic note or chord, to the final point of rest. What you have to do is determine what that tonic chord is in your song.

Now, this might be as easy as identifying the first or last chords of the song, as most songs begin and end in the key that they’re in, but sometimes the first chord won’t reflect the key. If that’s the case you’ll have to figure out which chords keep appearing in the chord progression, by eye or by ear. 

More often than not, the one that appears most will represent the tonic and therefore the key, but the big question you have to keep asking is, ‘which chord feels like home?’ Chances are that the chord that sounds like it hits the right note, bringing that sense of resolution, is the one demonstrating the key of the song.

Remember that even if chords appear that contain notes that are not in the song’s key – let’s say a D-major chord brings that F♯ to a C-major song – that won’t necessarily change the key. The F♯ should be treated as just an intrusive note that happens to not belong to the key.

Still unsure how to find the key of the song?

There’s every chance that you could be trying to find the key of a song that has a more complicated relationship with key, an issue that proves how simple a guide this really is. 

Let’s say that that D-major chord with its troublesome F♯ appears again and again, to the point that a C-major chord no longer feels like home. This could mean that the tonal centre has shifted to the key of D major. 

Yes, unfortunately keys can change even in the same song.

The reality is that key is just a temporary musical grounding in a certain tonality, and a lot of pieces of music move through several keys before they come to an end, especially in classical music. 

A work might be called ‘Concerto in B major’, but within the first few bars it might already have moved to a different key and not return to that original key - the home key, technically - for some time.

Sibelius’ Symphony No. 4, for instance, might be ‘in A minor’, but there’s only a whisper of that key at the beginning of the work, which then fades almost immediately.

How can keys change?

There are various ways in which keys can change in a song. We’re going to quickly look at a couple of those devices - modulations and key shifts

Modulations are carefully constructed passages of music designed to seamlessly move a piece from one key to another. E♭ major might feel like home one minute, but after a modulation B♭ major could be the new tonic, meaning that E♭ no longer feels like resolution, and that this new part of the song is in a different key.

Key shifts, on the other hand, are commonly used in popular music to inject some energy and drama into a song. In contrast to the delicacy of a modulation, a key shift involves basically dragging the music into a new key. Usually, the new key is a tone higher than the previous key, and it usually arrives for the final chorus.

How do I find the key if it keeps changing?

The hard truth is that some songs just don’t remain in one key. So if you’re looking to find the key of a song whose tonal centre keeps shifting, though you might be able to determine the key at a given point, that key won’t account for the entire piece of music. 

If you happen to find yourself confronting a piece like this - whether you’re reading sheet music or listening to a song - instead of asking what the key of the song is, a better question in these circumstances might be: ‘what key is the song in right now?’ 

Unless you’re dealing with a particularly difficult piece of music, using the steps outlined above, you now have all the tools you need to come up with the answer.

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