How to Tell if a Piece is in a Major or Minor Key

Welcome to LivingPianos.com, I’m Robert Estrin. The subject today is about how to know when a piece is in a major key or a minor key. There are certain sonic signatures you may already be aware of. Something in the minor key has more of a sad or dark quality than a major key. Just establishing a major key compared to the same exact chord progression in the minor key sounds drastically different. So you might be able to figure out that a piece is in a minor key because of the sadder quality that minor harmonies naturally tend to have. But is there a technical way to differentiate?

The key signature provides you with essential information.

If you know your key signatures, you know that if you have no sharps or flats that you’re probably in C major, if you’re in a major key. Because no sharps or flats form the C major scale. So what if that was in a minor key? What would that mean? Well, here’s the interesting thing about key signatures. All key signatures share both major and minor key possibilities. So if you have no sharps or flats, it could be in C major, but it might be in the relative minor of C major. What do I mean by the relative minor? It has to do with starting on a different note of the scale. The sixth note of the major scale is where the relative minor is found. So if you have no sharps or flats, instead of being centered on C, being centered on A, the sixth note of the C major scale, you are in A minor. Another way you can find the relative minor is to simply go down three half-steps from the major key. So once again, no sharps or flats could be C major, or it could potentially be three half-steps lower than C, which again brings you to A.

So what is the A minor scale?

The pure form of the A minor scale is simply the same exact notes of a C major scale, except starting on A. To discover whether a piece is in a major or minor key, you might think all you need to do is figure out where the notes are centered. There is actually a much easier way! Generally speaking, the minor is not found in its pure or natural form. Instead, it’s found in the harmonic or melodic forms, which have altered tones. That is to say that in a harmonic minor scale, the seventh note is raised a half-step. Interestingly, having a raised seventh makes an augmented second between the sixth and seventh notes. All the other notes of the scale are either half-steps or whole steps, but here you have a step and a half between the sixth and seventh notes.

Why is this so significant? Because if you see a piece with no sharps or flats, and all over the place you have G sharps, then you can pretty well assume that you’re in A minor. I mentioned that there’s a harmonic and a melodic form. The melodic form has two altered tones. Both the sixth and seventh notes are raised by a half-step. But the melodic minor scale descends in the natural form with no altered tones. There’s something really interesting about the melodic minor in that it has all the exact same notes of the major scale with the exception of the third. If you just change the third note from C to C sharp, now you have an A major scale. That’s an interesting side note, not to confuse the issue, because the A major scale has almost nothing to do with the A minor scale, except they are parallel major and minor.

Today the thing to think about is the relative minor.

Once again, the relative minor is found starting on the sixth note of the major scale. In C major the relative minor is A minor, which can be found in either the harmonic form with the raised seventh or the melodic form with the raised sixth and seventh, which only is ascending. Descending, it reverts back to the natural minor. So if you have a piece with no sharps or flats and you see a lot of F sharps and G sharps, you can be pretty well assured it’s not in C major, but it’s in A minor.

With other keys, as long as you know key signatures, you know which specific notes to look for. For example, if you have one sharp in the key signature, which would be an F sharp, this is the key of G major. To find the relative minor of G major, it’s exactly the same thing. It starts on the sixth note of the G major scale. Or you could go down three half steps from G. Either way, E minor is the relative minor of G major. So if you played all the notes of the G major scale, except starting on E, you would have the natural or pure E minor scale, the relative minor of G major. But that’s not the way minor scales generally occur. Usually, minor keys are found in the harmonic or melodic forms with altered tones. Both the harmonic and melodic minor have raised sevenths. The melodic also has a raised sixth. But the raised seventh is the keynote, because either of those altered forms will have a raised seventh. So the seventh note of the E minor scale gets raised by a half-step, which means the D goes up to D sharp. So if you have a piece with one sharp you might assume it could be in G major, which it very well might be. But you also want to investigate the possibility that it’s in the relative minor. Just count up to the sixth note of that scale to E, go to the seventh note of the E minor scale, which is D, and if you see a bunch of D sharps in your score, even though you’re in one sharp and you think you should be in G major, it could very well be in E minor. This is the way to really assess whether a piece is indeed in a minor key or a major key. Every single key signature has its associated relative minor starting on the sixth note of that major key, or going down three half-steps from the tonic note.

I hope this is helpful for you!

Study the scores of pieces you’ve played for years or pieces you’re working on. Check to see those keynotes. If you have a raised seventh in the relative minor, you’re probably in the minor key, not the major key. I hope this has taken a rather complex subject and broken it down for you so that you can investigate for yourself. It is extremely important to have the whole understanding of the score, the harmonies, and the structure. It can help with memory. It can help with sight reading. It’s not just an arbitrary exercise in theory. It has practical elements for you! I’m Robert Estrin here at LivingPianos.com, Your Online Piano Resource.

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