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Identifying the key


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Introduction

There are very many situations in music when you will need to quickly identify the key of the music. Let's find out how we can quickly and reliably do this.

Identifying the key

There are many possible keys for a piece of music. You won't have encountered all of the keys as yet, but there are plenty of them to learn - 15 major keys and as many minor keys! So you can't simply pick at random, and you'll have to develop your technique for identifying the key.

The technique here works by quickly cutting down all the possibilities to a few candidates, and then by a few simple steps eliminating all candidates except for one, which we then test for correctness.

Our method

Our method for identifying the key signature has five simple steps. We will look at each one in turn, in detail:

  1. What is the key signature?
  2. What is the note at the beginning and end?
  3. Are any triads outlined in the melody?
  4. Is the music in the major or minor?
  5. Test your ideas and come to a conclusion!

An example

In examining each of these steps, we'll refer to this short piece of music and try to work out what key it's in.

Q. In which key is this music written?

Q. In which key is this music written?Q. In which key is this music written?

1. The key signature

The quickest way to eliminate most possibilities is simply from the key signature. If we can correctly identify the key signature, we will have only two possibilities remaining, one major key and one minor key.

In the example, we can see that there is one flat in the key signature, and that's a B flat. Now, either you know your key signatures or you don't; if you do, then you'll know that this is either F major or D minor.

If you don't know your key signatures, or you just want to double check, then all you need to do is to apply that B flat to the natural notes, then see which note you need to start on to get the familiar major scale pattern:
T-T-S-T-T-T-S

You can also try checking on the pattern of the natural minor scale:
T-T-S-T-S-T-T

If you are still unsure that you've chosen the right major and minor keys, the other steps will either back you up or show that you were wrong to begin with!

2. Starting and ending notes

A piece of music will quite often start on the tonic of the scale (i.e., the "name note", the 1st degree; or G in G major, F in F major, etc.) Even more often, music will end on the tonic.

This is particularly the case if the music has harmony - the bass notes will almost always end on the tonic.

In this case, we have only a melody, but we can see immediately that the first note is A, and the final note is D. This suggests that our option of D minor is looking likely.

The dominant

Another note that a melody will often begin or end on is the dominant of the scale (i.e., the 5th degree). A bass line might begin on the dominant, but is extremely unlikely to end on the dominant. Very often, an opening dominant note will be immediately followed by a tonic note.

In this case, we know that the dominant of D minor is A, and the melody starts on the note A, and is followed by the tonic, D.

So D minor is still looking good!

3. Triads

Even though our example has no accompaniment, we can still look for harmony-related clues. Always have a look for a triad in your candidate key signature, in particular a triad on the tonic. In D minor, that would be the notes D-F-A, and we can see that straight away at the end of the music!

By contrast, we cannot see any triads on the tonic of F major (F-A-C). The only C we can see is a C sharp, and that won't do!

Again, our candidate of D minor is looking likely.

The right key

By this stage, you should be getting quite clear about what the correct key is. However, if you are still lost, then it may be that you picked the wrong key signature in the first step. Now is a good time to check.

Let's say that we'd picked the wrong key signature - and thought of B flat major and G minor by mistake.

Starting and ending notes?

The music does not start or end on either B flat or G! The closest it gets is D, the dominant of G minor, but the lack of the note G implies that this is not a likely candidate.

Triads?

We cannot see a triad on the tonic of B flat major (B flat, D, F) nor can we see one on the tonic of G minor (G, B flat, D), so once again, we have to consider that we might have picked the wrong candidate key signatures.

4. Major or minor?

The last step is really just to confirm what our suspicions are, as by now, we probably have only one very likely candidate (in our case, D minor).

We want to work out whether the music is in a major or minor key.

One thing we know about minor scales is that they have plenty of accidentals! In particular, accidentals on the 6th and 7th degrees. In D minor, we should therefore look for accidentals on B flat and on C.

We can see straight away that there is a B natural and a C sharp. This looks just like the ascending melodic minor scale in D minor!

By contrast, we know that major scales do not have accidentals that are not already in the key signature. Therefore, our other possibility (F major) is looking much less likely in this case.

5. Test your ideas

By now, we have formed a conclusion, that the key of the music is D minor. How can we test this, to double check?

The best question to ask yourself now is: do the notes in the music fit the scale of the chosen key?

Bear in mind that there are several possibilities in the minor key, but a phrase rising to the tonic will always have a raised 7th degree (and probably also a raised 6th degree). If the notes do not fit the scale of the key, then you might have the key wrong. Check back on steps 1-4 and see if another key fits.

The correct answer is...

The correct answer in this example question is, of course, D minor.

An advanced example

Here is a more advanced example, using a key signature which you won't have met yet - but you will do shortly!

Q. In which key is this music written?

Q. In which key is this music written?Q. In which key is this music written?

The answer

Here is the correct answer with working:

  1. Key signature? 4 flats - A flat major or F minor.
  2. Start/end notes? F in the bass, at both the beginning and the end, and F in the melody at the end. Therefore: F minor? (C in the melody at the start: could be the dominant of F minor?)
  3. Triads in melody? No, but the first chord is an F minor triad...
  4. Major or minor? E natural - the raised 7th degree of F minor - is present in several bars.
  5. Test! It looks like F minor - and the notes fit the scale. The B natural in bar 6 is the only exception, but is not repeated elsewhere.

Therefore our answer is: F minor

Another advanced example

Here is another advanced example, using another key you will come across in due course. The extra problem in this case is that we are not shown the ending of the music.

Q. In which key is this music written?

Q. In which key is this music written?Q. In which key is this music written?

Here is the correct answer with working:

  1. Key signature? 5 flats - D flat major or B flat minor.
  2. Start/end notes? No bass, and no ending ... the melody begins on D flat but B flat is prominent throughout... inconclusive, so far.
  3. Triads in melody? Not quite, but the fifth B flat - F appears early on, almost describing the tonic triad of B flat minor...
  4. Major or minor? The note A natural, which is the raised 7th in B flat minor, is present throughout, as is G natural. Bar 5 and bar 6 contain nearly all of the ascending melodic minor scale of B flat minor. The accidentals would not work for D flat major.
  5. Test! It looks like B flat minor - and the notes fit the scale, and we can clearly see the ascending melodic minor scale.

Therefore our answer is: B flat minor


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