Although there are some situations in which you don’t need to know what key a song is in, there are many others in which it’s beneficial and even critical to know.
If you’ve been called upon to improvise on stage, for instance, and you don’t know what key the song is in (and no one tells you), you’d be left to try to figure it out for yourself.
You might even end up having to stumble through the song, which can be embarrassing.
This has happened to me many times, and it could happen to you too (you just never know when you might be called up on stage to jam).
If you have a solid strategy for figuring out what key a song is in, in case the need arises, you’ll be better equipped to handle anything that’s thrown at you.
Here are the many methods people use to determine a song’s key signature, the advantages and disadvantages of each, and how to use them.
But before we get started, there’s one question we need to answer:
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Why Would I Want To Figure Out What Key A Song Is In?
You can probably offer a better answer to this question than I can.
But let me help you out.
If you’re trying to figure out a song in any capacity, knowing what key it’s in can be incredibly helpful.
If you were attempting to transcribe the song, for instance, before you even wrote down one note, knowing that the song is in the key of Bb (for instance) would help you figure out the chord progression, melody and harmony with greater ease.
Most songs are based on diatonic (seven note) scales.
There are only 12 notes in music, but I’m sure you can see how narrowing that down to seven would make your life a lot easier.
Another situation in which it’s helpful to know what key a song is in is if you’re a lead player and you’re going to be playing fills, licks and solos over it.
Knowing what key the song is in would give you a good of idea of which notes you can play, even which notes you’d want to play.
With that, it’s time to get into the various methods people use to figure out the key signature of a song.
Tell The Key By Listening For The First Note Or Chord In A Song
It seems like this would be a solid method for determining what key a song is in, and although many times it is, it isn’t 100% reliable.
I’ve even had younger guitarists come and ask me if this is how they know what key a song is in, and I answered, “no, watch out – this could lead you down the wrong path.”
I would be steering them in the wrong direction if I told them otherwise.
Guitarists are often given opportunities to play leads and solos, regardless of context (it could be at a jam, church service, bar gig, in the studio or otherwise).
So, knowing what key a song is in can help a player figure out what kind of color or texture they want to add to a song.
Conversely, not knowing what key a song is in could either limit what the guitarist plays or leave them confused enough that they don’t play at all.
Here’s a great example of where things could go wrong if you assumed that the first note or chord in a song was all you needed to figure out what key the song is in.
Harem Scarem’s “Jealousy” is in the key of Eb minor, and yet it begins on a Bb7 chord.
As guitarist Pete Lesperance begins to jam out riffs using the blues scale, it becomes more apparent what key the song is in.
But if you had assumed the song was in Bb, based on the intro, you would have been led completely astray (further, the fact that it was a dominant chord probably would have thrown you off – you may have assumed it was a jazz or blues song – “Jealously” is more of a hard rock/funk song).
If you had guessed based on the fact that Bb7 only belongs in the key of Eb, you would have come closer. But again, the song is in Eb minor and not Eb.
Many times, songs are simple enough that we “get lucky”, for instance, when we guess that a song is in the key of E because of the first chord and it happens to be E, as expected.
But what other keys do we know that also have an E chord in them?
Well, there’s A and B major just to name a couple.
That means the song could have been in A or B, and you just happened to guess correctly that it was in E.
Another possible outcome, of course, is that the song isn’t in the key of E, A or B, so paying attention to the opening E chord would only throw you off.
So, don’t be too hasty in assuming the first chord tells you everything you need to know about a song.
By Listening For The Last Note Or Chord In A Song
Okay, so if listening for the first note or chord in a song isn’t 100% reliable, then listening for the last note or chord in a song must be, right?
I see people make this mistake all the time, and sorry to say, it’s not an ironclad solution either.
Again, some of time, you will be right, but not always.
In case you hadn’t noticed, there are no guarantees that a song will end on the root, and many times it doesn’t!
It became relatively trendy in the 90s and early 2000s to end songs on suspenseful chords (oftentimes the IV chord).
I, for one, use this technique in my music more than I care to admit.
See, there’s no requirement or rule stating that a songwriter or producer must bring resolution to a song by landing on the root at the end – they don’t!
Not being required to do so means the ability to end the song on any chord of their choosing – even one that’s outside the original key signature (seriously).
Maybe it flies in the face of classical composition technique, or some conventions that are taught in school, but it doesn’t go against modern songwriting technique in the least.
Matchbox Twenty’s “3AM” is the perfect example, with the song ending on the IV chord rather than the expected I.
And, there are plenty of other songs that do the same if you go looking for them.
If you dependably knew that the song was ending on the IV chord, then you could make the argument that you could easily identify related keys, and know (within a margin of error), what key it’s in.
Unfortunately, you don’t, because again, there are plenty of songs that end on unusual chords, sometimes completely outside of the spectrum of related keys.
My recommendation would be to do a thorough analysis of each chord progression in the song first, which should offer some good clues as to what chord the song is ending on.
You’re just guessing if you’re doing this backwards.
Find A Song’s Key By Using The Circle Of Fifths/Fourths
This would be the best Sunday school/goody two shoes answer if there ever was one.
The circle of fifths is a valuable tool for identifying the various key signatures that exist, the relative minors and how many sharps or flats that are in each key.
But if you were on stage right now, the band started playing, and you didn’t know what key the song was in, the circle of fifths wouldn’t be of much help.
In a situation like that, visual cues would offer more help than the circle of fifths diagram (e.g. if you were able to figure out what notes the bass player was playing, what chords the keyboardist is playing, etc., you could figure out what key the song is in).
Further, what if I just put a random song on right now and asked you to figure out what key it’s in only using the circle of fifths?
Unless you have perfect pitch, you’d be on a boat without a paddle.
So, if you didn’t know what key the song was in, the circle of fifths would be almost entirely useless.
Where it might come in handy is if you knew what key the song is in but didn’t know how many sharps or flats the scale has, because you could use the circle of fifths to figure that out.
Using the diagram, you could quickly figure out how the scale is constructed.
By Analyzing The Lead Sheet/Music
Assuming the band leader didn’t call out a key (if they did, you probably wouldn’t be reading this guide), I would suggest that this is the most reliable way to determine what key a song is in.
If you aren’t good at reading a lead sheet or sheet music, or if you don’t know your scales and key signatures, then you might still be in trouble and need to take a few music theory lessons (seriously).
Otherwise, taking a quick glance at the chords used in a song can give you a good idea.
If I saw these chords, I would instantly know what key the song is in (would you?):
A | A | B | B | C#m | B | A | A | F#m | A
If you looked at the first and last chord, you would assume it’s in A, right?
Again, this only serves to highlight the limitations of the method, because A would be incorrect.
If you knew what number the chord was, you could probably figure it out – only, this information isn’t always readily available, as in this example.
So, think carefully here.
B major doesn’t belong in the key of A, does it?
For it to be solidly in the key of A, that B would have to be a Bm instead.
And, that’s because this progression is in the key of E.
Did you guess it right?
If were to use the numbering system, it would be this:
IV | IV| V | V | vi | V | IV | ii | IV
It’s okay if you didn’t get this right away, even if you know your theory.
This stuff takes time, and it may only come through practice and experience.
The key is to get good at quickly analyzing the music in front of you and knowing what notes belong in what key (which is something the circle of fifths can help you with).
If you’re looking at sheet music (which doesn’t always include chord markings), then the only thing you’d need to observe is the key signature marking on the treble clef (again, if you don’t know how this works, you’re hooped).
You could analyze the melody in the song as well (and we’ll be looking at this method a little later), but that seems excessive, and it could even throw you off track because of accidentals.
Sheet music generally makes it easy for you to know what key a song is in.
If you haven’t got a hot clue what I’ve been talking about in this section, then it’s time to brush up on your music theory.
By Analyzing The Song’s Chord Progression You Can Find Out What Key A Song Is In
This method is basically the same as above and is nearly 100% dependable.
But instead of relying on the totality of the music (chords, melody, harmony, bass line, etc.), you would instead rely on the chord progression alone to figure out the key.
Assuming the chord progression has been written out, and you have access to it, and you know how to analyze it, you should be good to go.
If all you have is sheet music, as already noted, it may not include chord markings, in which case you’d be required to analyze the music and determine the chord changes yourself.
This is a valuable skill, but I’ll be honest – even I have trouble with this.
I knew people who claimed to be able to determine chord changes based on sheet music, and even they did it poorly!
So, if you don’t already have the chord progression for the song, you’ll probably need to choose a different method.
Anyway, let’s look at another example of a rather tricky chord progression:
Gm | Am | Dm | Dm | Bb | C | Gm | C
Again, if you thought that you could figure out what key this is in just by looking at the first chord or last chord, you’d be in trouble.
I can tell you right now it’s not in the key of G minor and it’s not the key of C major either.
A minor may have been your next guess, but since it’s the relative minor to C major, that can’t be it.
Knowing that, there aren’t too many possibilities left, and by process of elimination, you may have figured it out already.
I’ll give you the numbers before I reveal what key this chord progression is in, although if you know your theory, this will certainly give it away:
ii | iii | vi | vi | IV | V | ii | V
Did you figure it out yet?
This song is in the key of F major.
If you answered D minor, you would also be correct.
To use this method, you would need to have a strong foundation in theory.
With that in mind, it is a reliable method.
Songs can sometimes have “outside” chords or key changes that will throw you off a bit, but assuming you know what you’re doing, you should be able to navigate these minor inconveniences.
If I’m not thinking clearly, then sometimes chord progressions can throw me off, but most of the time, this method works just fine.
By Analyzing The Song’s Melody
Again, this is like analyzing the sheet music to determine what key the song is in (which is typically simple, because you can just look at the key signature marking).
In most cases, you won’t need to analyze an entire song’s melody to figure out what key it is in – just looking at a small segment can be more than enough.
If you have the key signature marking in the sheet music, it’s completely unnecessary.
It is, however, a reliable method.
Something we know about melodies is that they are created using scales.
And, most melodies are created using just one scale, even if that scale sometimes includes accidentals.
If we can figure out what scale the melody is made of, we should be able to get a good idea of what key the song is in.
Note that many melodies are simple and rely heavily on “safe” notes, so sometimes this doesn’t always give us all the information we need to know to determine a song’s key signature.
The same “safe” notes could appear in other scales, which is where things can get complex.
But let’s say you’ve identified the notes the singer is singing.
And, we’ll say they’re singing these notes:
G, G, G, C, G, D, A, D, G, C, E, Eb, D, G.
I’ve chosen these at random, so they don’t necessarily make for a great melody.
If there wasn’t an Eb, we could safely conclude that it’s in the key of C.
Though, in this case, the Eb looks like a passing tone connecting the E to the D, so we can’t entirely rule out C.
But based on the repeated G and C notes, I would be more inclined to say it’s in the key of G (and, I wrote it with G in mind).
Even though there is no F# to spell it out without a doubt (the F# would tell us definitively that it’s in the key of G), the order of notes and the specific ways in which they connect with each other would tell me it’s likely in the key of G.
But this is exactly what I mean when I say “safe” notes.
Pop music tends not to deviate too far from notes that sound catchy and consonant, which usually means sticking to the five-note pentatonic scale rather than the diatonic counterpart it was derived from.
Though it often leaves some room for interpretation, sometimes analyzing the melody can be helpful when trying to figure out what key a song is in.
By Improvising Over The Chord Progression
This may sound unorthodox, but honestly, there have been countless times I’ve had to jump on stage and improvise to figure out what key the song was in so that I could offer my services as a lead guitarist.
And, when I’ve had to do this, I usually just started by playing a note or two to figure out where things were going.
Generally, by the time I’ve played one or two notes that belong in the key (which is usually instantaneously), I know where to go from there.
It helps that I’ve got a good, intuitive sense of what key a song might be in before I even play the first note.
On the guitar, scales are all movable patterns, so once you’ve learned one scale, you’ve basically learned that scale in all keys.
So, once I’ve identified what pattern I’m playing in, I’ll be able to figure out what key it’s in.
Naturally, it’s always best if you aren’t required to go on stage and make a bunch of mistakes before you figure out what key the song is in.
This can come across as unprofessional to the audience, and the band could get angry at you besides.
I haven’t had that problem, but I’m not saying you won’t.
In a risk-free scenario, like at a jam, however, you can generally make as many mistakes as you want.
How To Tell What Key A Song Is In, Final Thoughts
If you don’t have a strong foundation in music theory, trying to figure out what key a song is in is going to prove an uphill battle.
In this guide, I’ve given a couple examples of chord progressions, but honestly, they can get even more complex – especially in genres rife with chords and key changes (jazz or prog, for instance).
So, my main piece of advice here would be to spend more time studying music theory, especially if you’re a little unsure how this all works.
We’ve got a lot of great guides right here on Music Industry How To, so start browsing now and upgrade your knowledge – it will undoubtedly help you on your musical journey.