How to Find Your Key (in a piece of music)

The single most common question I receive from piano teachers around the world revolves around the issue of knowing what key one piece or another might be in. Composer-colleagues writing for piano students often find messages in their in-boxes, too, from teachers who want to be sure they’ve told their students the right thing before the student sits their piano exam…

One part of the problem is that piano teachers, and their students, for various reasons, generally assume that there are no other possibilities beyond the 12 major and minor keys when answering the question “in what key is this piece of music?”.

This problem is then exacerbated when a teacher or student tries to figure out the key simply by looking at the key signature (and not bothering to think about what the music sounds like).

From the time of the last decades of the 20th century, the compositional and notational practices as regards tonality require a new approach to the one musicians are trained in when they learn traditional music theory, not least because one of the most common notational choices of composers these days is to not use a key signature at all – accidentals are just inserted as required!

Another common notational choice made by contemporary composers is to use the key signature that most closely relates to the notes being played in the piece. So if a piece is ‘minor’ but consistently needs the 6th to be raised (in other words, if it’s in the Dorian mode) then a composer will often choose to use the key signature that doesn’t flatten the 6th. Seems logical, doesn’t it? No need to use an accidental whenever that 6th degree is played – far more efficient! You might be seeing three sharps, but the piece is “in” B (Dorian). Or you might see no sharps or flats and thus feel safe announcing that a piece is in C Major, but it’s really in G (Mixolydian)!

What’s a teacher trained in 19th century theoretical practice to do?

How can you tell, in this day and age, what on earth key you are in, if it’s not the key of the key signature?!

HOW TO FIND YOUR KEY (almost all of the time):

Step One: Look at the first left hand note of the piece, and look at the last left hand note – are they the same? 
Yes? You have at least a 99.575% chance that this note is the tonal centre of the piece!
No? OK, so let’s just look at the final left hand note of the piece – you have at least an 94.92% chance that this note is the tonal centre.
Still feeling a bit uncertain? Let’s go to the next step…

Step Two: Play the piece through. When you get to the end ask yourself: which note feels, to you, like “home”? 
Is this the same note as the note you picked in step 1?
Yes? There’s a 99.9895% chance that this note is the tonal centre.

If your student is sitting an exam at the earliest levels this might be all you really need! Your student needs to say “the tonal centre is {name of note}” and all will be well – examiners do not expect Grade 1 and 2 students to be up on all their modes, by any means, and they certainly don’t expect them to be able to explain things more complex again!

Step Three: Now you have a tonal centre you need to decide if the piece is more major-sounding, or more minor-sounding, and listening is the fastest way to figure this out.

Does the piece sound major, or minor, to you? If you feel confident about this answer (and you probably will be perfectly confident!) – jump straight to step 4.

Feeling as if you can’t trust your ears? It’s time to look at the score. Find the note a 3rd above the tonal centre key in the notation. Is this a major 3rd above, or a minor 3rd above? [For example, in C the major 3rd above is E, but the minor 3rd is E flat.] The answer to this question tells you whether you are in a major mode or a minor mode.

Do you see both the minor 3rd and the major 3rd? You’re almost certainly in a MAJOR mode, and the other note is just bad ‘spelling’!

Step Four: You now have a tonal centre (the letter name) and a tonal orientation (major or minor), and it’s time to get to the nitty-gritty – what mode is the piece in?

The presence of a key signature is a pretty good sign that the music is in a mode of the major scale pattern [Dorian, Phrygian, Lydian, Mixolydian – the Aeolian is already taken as it is the “natural minor” and uses the theoretically appropriate key signature]:
Major-sounding music:
IF the key signature has one less sharp/one extra flat than you were expecting: you are in the Mixolydian mode.
IF the key signature has one extra sharp/one less flat than you were expecting: you are in the Lydian mode.
Minor-sounding music:
IF the key signature has one extra sharp/one less flat than you would see in the minor key signature: you are in Dorian mode.
IF the key signature has one less sharp/one extra flat than you would see in the minor key signature: you are in the Phrygian mode.

Step Five: But maybe the music has no key signature at all. This doesn’t mean you’re not in a mode listed above! But you’ll need to do a bit more detective work. Bear in mind the rules for key signatures listed above, and apply them to the accidentals you see recurring throughout the work.

Step Six: Remember that some accidentals are for colour, and that’s all – so you will be needing to use your judgment!

If there is a raised 4th AND a perfect 4th in the music it is the raised 4th that is the “colour”. This is very common, and probably the source of most confusion amongst teachers seeking answers regarding keys of contemporary pedagogical piano music. When you play the music through be thinking very carefully about whether that raised 4th ever resolves to a perfect 4th – or not!

If there is no perfect 4th then you’re probably in the Lydian mode or in the Lydian Dominant (what I prefer to call The Simpsons Scale). The difference between the two? The Lydian Dominant also has a flattened 7th. Both have a major tonic triad.

By way of contrast: if there is a flattened 7th AND a major 7th occurring regularly in the music it is almost certainly the major 7th that is the “colour”!  You’re in the Mixolydian, Dorian, Phrygian, Lydian Dominant, or some other mode with a flattened 7th.

Step Seven: What about when it’s something else, again? In truth, there are still plenty of other options, but by now we’re getting into far less frequent occurrences in pedagogical piano literature! But there’s one more thing well worth looking out for, even if you mostly teach students at the elementary and early intermediate levels….

This final, most common cause of key confusion? When you have a flattened 2nd AND a major 3rd.

This combo means you’re almost certainly in the mode of the 5th degree of the harmonic scale – which means you have a flattened 6th and 7th as well. The tonic triad of this mode is a major chord, but you still get the feeling that you’re in a minor key – kind of! The music is often described as being Spanish, or flamenco, or gypsy, or Middle Eastern. This mode has many, many names, because it occurs in so many cultures: the Phrygian Dominant, the altered Phrygian, the Spanish Phrygian, the Freygish, the Vakulabharanam (a Carnatic raga), and many others besides. It’s a super cool mode, and worth becoming familiar with – once you know what you are looking for you’ll start to see it quite frequently.

But remember that it’s steps 1 and 2 that are the most important: be confident in locating your tonal centre, no matter what. This sets both you and your student up brilliantly for further exploration down the track. And don’t feel compelled or bullied by 19th century music theory expectations – music from the 21st century isn’t going to be a natural fit for rules from more than a century and a half ago, unless it’s music that doesn’t sound particularly ‘now’!

The very most important thing is to know where home is. Something that’s true even when we’re not talking about music….

20 thoughts on “How to Find Your Key (in a piece of music)

  1. Thank you so much, Elissa! I have been looking for something like this for awhile now. My students start with the technique & patterns of the piece, usually before looking at it, & are starting to play scales in these modes. Rather than have to enter notes into an online calculator (& then still have to guess which one) this will be a great tool when planning & teaching!

  2. Elissa, I have gradually learned to wrap my mind around mode identification in various ways, through the years. But the ‘IF the key signature has one less sharp/one extra flat than you were expecting: you are in the Mixolydian mode’ principles are a new way of perceiving modes for me. Very cool! I admit I’m going to have to go to the piano to fully grok the Spanish Phrygian……. BTW Forrest Kinney has some great modal pieces in his Pattern Play books. Also one of his older volumes, hopefully still available on his website, is called ‘Modes’ and contains close to 100 improv patterns using modes. Thanks for the clear laying out of the mysterious-to-many modes and keys.

    • Oh, and I also loved your firm, confident percentages (99.575% …. 99.9895%) for the chance of having found the tonal center. These are based on serious research, I’m sure. 🙂

      • 🙂 I think it’s quite important to back these things up with numbers. 🙂

        … I was wondering if anyone would query these!! hehehe 🙂

  3. Very well laid-out and thoughtful–and not the least bit condescending to those steeped in 19th century practice. As we teach more and more repertoire from living composers, it’s vital we teachers be able to know the playing field and talk intelligently about it. Thank you!

  4. During my brief foray into playing (folk/lever) harp a few years back, I used to experiment with ‘modes’ by randomly raising sharping levers over the various octaves. I kept my harp tuned to Eb, so was able to create both ‘naturals’ and ‘sharps’ by raising the levers. Very fun! And something we can’t really do on piano.

      • The original inspiration for doing this came one day when I was sitting out on my back porch, enjoying the early spring sunshine and playing some too. A little breeze came up and brushed the strings of my hair — voila! Aeolian harp music! That gave me the idea to just randomly change a few levers and see what sounds resulted. I never got very good on the harp, but one huge benefit of even my feeble efforts was a loosening of my ‘traditional 19th century’ paper-trained inner strictures and a feeling of freedom to improvise!

  5. Thank You Elissa! (sigh….) After leaving so much harmony at University after teaching music in High School, and early childhood music for more than 20 years, the modes require some brushing up. Steps 1-3 are sound, so I really appreciate this confirmation that I’m on the right track. With your kind direction the brain can work out the rest. It seems all is not lost! (Whew!)

  6. This is a wonderful and informative article Elissa.
    I agree with your approach wholeheartedly.

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