The concept of keys itself isn’t too daunting. Most students I’ve taught have an easy enough time grasping the concept that each key contains seven specific notes that all work together, and that those seven notes can be arranged to form a specific set of chords unique to that key. However, what seems to give musicians more of a challenge is knowing exactly what key they are in. Those with a strong knowledge of theory can analyze a chord progression or other piece of music and determine its key, but that is often much easier said than done. Looking at music analytically often isn’t an option yet for students still working on honing their music theory chops, and isn’t entirely applicable to songwriting trying to determine the key of pieces of music that aren’t entirely written yet. If this describes you, then this article may be of help to you. 

In this piece, we are going through a step-by-step process to determine the key of a piece of music entirely by ear that is friendly to musicians with little-to-no music theory knowledge. In order to use this process, you will have to have an instrument with you and some way of playing the music whose key you’re trying to determine. If the music in question is a pre-existing song then all you’ll need is some sort of media player capable of playing the song. If you’re trying to determine the key of a vocal melody you’ve written that doesn’t have chords yet, then you can try singing the melody while testing out the key notes on your instrument (more on that later). If you are trying to determine the key of something you wrote on your instrument, such as a chord progression or riff, then I recommend recording the music in question on your phone or other device and testing out the key notes over the recording. Once you have your specific citation all figured out, then you’re all ready to go!

Some quick notes before we start: this process is geared towards diatonic keys, which are the most common kind. If the music you are analyzing is written in a less common kind of key, such as a harmonic minor or a blues, then you may find some issues with the system. Additionally, many songs based on diatonic keys will have occasional moments where they use notes from outside the key. It’s up to you to use your ear and your judgement if you think the music in question sounds like its maybe venturing outside of the key that most of the song is in. If so, you may want to use a different part of the song for this process. 

A short final note is that this piece determines a song’s relative major key. Your song may be in a minor key or other mode. If you feel like this is the case, you can look up the name of that mode after determining its relative major key. If none of those quick notes made all that much sense to you, then don’t worry about it. They are primarily there as disclaimers for outlying pieces of music anyway.  

A Sharp Key, A Flat Key, Or Neither?

The first step is to determine whether you are working in a sharp key, a flat key, or the one key that is neither.  Start off by playing an F-natural note repeatedly over the piece of music. If the note clashes, then that means you are probably in a sharp key, thus limiting the possible keys to G, D, A, E, B, and F#. This is because the F-note is the first note to become sharp in sharp keys, so there is no natural key with sharp notes but not an F#. If the note does not clash, but instead feels at home with the piece of music, then that means you are either in the key of C major, or in a flat key. 

If this is the case, then your next step is to play a B-natural note over the music. If both the F-natural and the B-natural blend smoothly with the song, then you’re in the key of C-major. This is because while F is the first note to become sharp, B is the first note to become flat in flat keys. C-major is the only key with no sharps or flats, meaning that it is the only natural key with both an F-natural and a B-natural. If the B-natural clashes with the music but the F-natural does not, then that means you are in a flat key (the reasons for that are discussed above). The natural flat keys are F, Bb, Eb, Ab, Db, and Gb, meaning that if you’re dealing with a flat key, you’re dealing with one of these. 

If You’re In C

If both the F-natural and the B-natural work with the music, then it’s a pretty safe bet that you’re in the key of C. You can double check this by playing sharp and flat notes over the music and making sure that they clash, but that’s really just in case you’re unsure. Otherwise you’re in the key of C, so congrats, you’re done! That was quick, wasn’t it?

If You’re In A Sharp Key

If you’ve determined that you’re in a sharp key, then you’ve completed the first big step. Your next move is to determine exactly which sharp key you are in. As mentioned before, the sharp keys are G, D, A, E, B, and F#, meaning that you will be in one of these keys. In order to determine exactly which of these keys you are, try playing the note that becomes sharp in each key over the music in question. Don’t worry if you don’t know what those notes are; we’re about to go through them one by one. 

A quick note: Key signatures are cumulative. We start in the key of C, which has no sharps or flats, and either accumulate sharps in the sharp keys or accumulate flats in the flat keys. Therefore, the sharps or flats we accumulate in one key will carry over to the next key. Will get more into that later, but for now we will simply look at the sharp keys in the proper order for the notes to carry over. 

The key of G is the first key to have a sharp, meaning that it has only one sharp. That sharp is an F#, which is the one note all sharp keys have in common. If F# is the only sharp note that works with your piece of music, then that means you are in the key of G. However, in order to know that F# is the only sharp note that works, you’ll first have to try out at least one other. 

The sharp key that follows G is D, which contains both an F# and a C#. As you have already confirmed that an F# works with the music in question, try playing a C# over it. If the C# clashes, that means you are in the key of G. If the C# does not clash, then that means you are not in the key of G and can rule it out, leaving you with the possible keys of D, A, E, B, and F#. If the C# did not clash, then the next note to try is a G#. If the G# clashes, then you are in the key of D. If the G# does not clash, then you can rule out the key of D, leaving you with the possible keys A, E, B, and F#. 

If you still haven’t found the key yet, then the next note to try is a D#. If the D# clashes, then you are in the key f A, and if it doesn’t then you can eliminate the key, thus leaving you with the possible keys of E, B, and F#. The next note to try is an A#. If the A# clashes then you are in the key of E, and if it doesn’t then you are down to only two possible remaining keys: B and F#. If you made it to this point, then you’re probably in the key of B for two reasons. The first is that the key of F# is pretty rare, and the second and bigger reason is that the key of F# contains an E#. E# is the enharmonic spelling of the note F, which you already determined clash with the music in question in the very first step of this process. 

I know that was a lot, so some of the above information has been condensed into the following chart for easy reference: 

If You’re In A Flat Key

If you’ve determined that you’re in a flat key, then the process is pretty similar to that of being in a sharp key. As mentioned before, the natural flat keys are F, Bb, Eb, Ab, Db, and Gb, so you’ve already narrowed your options down to one of these. To figure out exactly which of these keys you are in we’re going to play the note that is flated in each key over the music in question, thus eliminating keys until we’re left with whichever key matches your music. You’ve already determined that B-natural clashes with the music in question, but a good way to double check that it’s in a flat ket is to play a Bb note over it. Every flat key contains a Bb, so the Bb should blend smoothly with the rest of the music. 

A quick note: Unlike sharp keys, the notes used to test flat share names with many of the keys flat themselves. For example, a Gb flat note can be used to determine if you are in the key of Ab, and an Ab note can be used to determine if you are in the key of Bb. This can lead to quite a bit of confusion if you don’t read carefully, so please watch out for that! 

 If Bb blends with the music in question, then the next note to try is an Eb. If the Eb clashes with the music, then its in the key of F. If it doesn’t clash then the key of F can be eliminated, leaving you with the possible keys of Bb, Eb, Ab, Db, and Gb. After Eb, the next note try is an Ab. If the Ab clashes then you are in the key of Bb and if it doesn’t, then the key of Bb can be eliminated which leaves the remaining keys of Eb, Ab, Db, and Gb. After Ab, the next note to test over the music in question is Db. If the Db clashes with the music, then you are in the key of Eb, and if it doesn’t then you are left with the remaining keys of Ab, Db, and Gb. 

The next note to try over the music in question is a Gb. If the Gb clashes, then you are in the key of Ab. If it doesn’t then the key of Ab can be eliminated, leaving you with the remaining possible flat keys of Db and Gb. Now that you’ve narrowed it down to only two possible keys, there is only one note left to try: a Cb. If the Cb, which is better known by its enharmonic spelling B, clashes with the music in question, then you are in the key of Db and if it doesn’t, then you are in the key of Gb. 

Just like the sharp keys above, some of all of that has been condensed into following chart: