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How Can We Tell Which Key We’re In?

This post is one of a growing series of holistic investigations into various aspects of music theory. The full list can be found in the Posts page under the category Music Theory De-Mystified.

All comments are welcome. If you enjoy my post, please give it a like and share it or subscribe to my blog.

First I should say that there are two separate subjects here: the overall key and the key at a given point in the piece such as a visiting key. For the purpose of this post I’ll focus on overall key and assume a fairly simple melody but in principle, the same applies to sections and even individual phrases within the piece.

If you’re looking for a quick answer, scroll down to the summary.

When we play a scale, it’s easy to tell what the key is: it’s a combination of the root note and the mode. If we start and finish on C and play the major scale pattern of .2.2.1.2.2.2.1. (semitones), we’re in C major: C major is the major mode built on C.

But how can we hear/feel what key we’re in when the order of the notes varies, as in a melody?

If you’re reading notation, you could say, “look at the key signature”. This is true, but it’s only part of the answer. Within a key signature there are many possible tonalities. Even considering only the major and minor modes, you still need to find the right choice, to help interpret the music correctly. And if you’re listening or playing by ear, you need to be able to “feel” the key.

Look for the root note

To do this, we need to know what the root note is. For a given key signature (set of notes that make up a scale), the mode is determined by where we start the pattern i.e. the root note.

“The Spokes Of A Scale”

The best way to think of a scale is not as a strip of notes lying next to each other but as a series of spokes with the root note at the centre and the other notes around it. The double lines in the following diagram indicate the special bond between the root note and its octave (where the pattern repeats) and between the root note and the perfect 5th (more on that later in this post).

(…I see it as a kind of spiral staircase extending up and down the octaves like storeys of an apartment block, where notes on the central column are octaves of the root note…)

Root Note Power

In a piece of music, it’s as much about the relationship of each note to the root note as it is from each note to the next. To be able to feel the key we need to be able to feel the root note.

There’s a good chance that the root note is first, or at least among the first few notes, and also at or near the end, but it’s not always the case. Fortunately there are many other ways it can be pointed out in a melody.

Longest, Strongest and Most

In a melody, other than first and last, these are the three main ways we can highlight the root note.

Longest

Duration is power. Out of a series of different length notes, the longer notes are more prominent. If the root note is a long note it will stand out in the crowd.

Strongest

One way to emphasise the root note is to give it strength. There are two ways to do this:

by playing that note louder than the others or giving the note an accent (a strong attack).
by making the root note appear on the strongest parts of the bar. Time signatures have an implied hierarchy of strong and weak points- a default rhythm, if you like. Placing the root note on beat 1 gives it the most strength. In 3/4 and 4/4, beat 3 is also naturally strong. Similarly, on-beat quavers are naturally stronger than off-beat quavers.

Most

Another way to reinforce the root note is to keep coming back to it. The more often we hear it compared to surrounding notes, the more we believe it.

Examples

Here are a few single-phrase “melodies” using just a single technique to highlight the root note. For the following examples, as you listen, try to hum the note that feels like the root note. Bear in mind that no single note will fit all the time. What we’re looking for is the note that fits most of the time. When you stop listening, which single note would you remember? Try a few if you’re not sure…

The examples are all in C major, so if the techniques I have described are effective, C should feel like the root note.

To make it a fair test, I have tried to make the (mini) melodies fairly random apart from the parameter we’re testing, so they’re not great. Real composers use a combination of these techniques when creating a melody.

Longest

Strongest

Most

Lowest & Highest, Direction

Although not as significant overall, the lowest and highest notes of a passage within the melody will be naturally emphasised. I see this more as a sense of direction. When listening, we follow the direction of a scale-like series of notes, upward or downward, to its destination. The series directs us to the destination, giving that last note emphasis, before changing direction.

A scale played ascending then descending is as good an example of this as any. Scales are essentially very simple melodies with no detours.

Lowest, highest, direction

Harmonic Reinforcement

The perfect 5th, a great support act

The 5th note of a scale is almost as special as the root note itself and warrants a post of its own. I will say that it has both the capacity to blend well with the root note to support it (even if the notes are one after the other rather than played together) and to be a convenient destination for the melody to visit, a temporary root note of its own.

As a supporting note it is second to none. A 5th nearby will reinforce the presence of the root note by “pointing to it”. The 3rd note, especially the major 3rd, can also help in this way.

Some melodies place all 3 notes of the home key’s triad (chord) near each other, virtually acting as an arpeggiated chord, providing an even stronger emphasis.

Harmonic reinforcement from the perfect 5th

Accompaniment

We haven’t talked about chords yet. Chords have an enormous say in what feels like home. Chords (at least the basic types) feature the three most important notes of a key, the 1st (the root note), the 3rd and the 5th. These notes blend so well together that they reinforce the chord’s root note.

While the chord sounds (if it sounds for long enough), it’s hard not to feel that its root note is, temporarily, the root note of the piece.

The most prominent chord overall, especially towards the beginning and end of the piece, is generally that of the home key.

Other chords can also feel like home for a while if they sound for long enough, providing visiting points in the melody. This is one of the tools a composer can use to create music that has a journey, a sense of going places, rather than being stuck at home the whole time like a COVID lockdown.

The techniques described in this section are also used to establish the new key after a modulation (key change).

Even when no chords are played, the melody’s sense of direction and use of the above techniques can suggest some of these temporary keys. Chords can also be played melodically, as a series of notes called a triad. Many melodies are largely made up of scale-like passages and triads.

In A Nutshell

To answer the title question: look for the root note. The music makes sense when you can hear/feel how the other notes relate to the root note.

Look for a strong note or a strongly supported note early in the piece and towards the end. Feel the flow of the melody’s phrases- where the phrases start and end, which notes are emphasised. When a phrase is arriving home, you will hear it.

Once you know the root note, the mode will become evident, because you’ll interpret the other notes from the root note’s perspective. You can confirm this by playing the notes of the melody as a scale starting on the root note. If you have chosen the root note correctly, the tonality of the scale will match the overall tonality of the piece.

Much of the content is based on my upcoming music theory reference, Music Theory De-mystified, which is currently planned for release as an e-book by the end of 2022.

Please feel free to comment. I have a slightly unorthodox way of presenting music theory concepts but the concepts themselves are well established. If you like my posts, please subscribe so you can be informed of new posts.

A Melody Is A Journey

This post is one of a growing series of holistic investigations into various aspects of music theory. The full list can be found in the Posts page under the category Music Theory De-Mystified.

All comments are welcome. If you enjoy my post, please give it a like and share it or subscribe to my blog.

This is a key tenet in my approach to music theory. However, if you disagree, feel free to comment.

Most music has both a melody and chords. Even a melody by itself is usually built on chords, it’s just that we don’t hear them. We call this an implied chord progression (when no chords are written, we can deduce the likelihood of potential chords by the evidence provided in the melody such as phrase structure, the actual notes used and the use of accidentals).

A chord represents a key- at least basic major and minor chords and their common variants do. How effective they are at establishing their key depends on low long they’ve got. Yes, time. The longer the time spent on a chord, the more it feels like THE key.

A melody is a journey. Typically it starts at home (in the home key) then travels to one or more visiting keys, represented by the main chords along the way, eventually arriving home again.

Just like a physical journey, the trip can be long or short, fast or slow, bumpy or smooth, visiting nearby or exotic places on the way. Everything that applies to a physical journey has its parallel in a musical journey.

There are three parts to any trip- the departure (including any prep such as packing), the travel and the arrival. Similarly, pieces (and the phrases within them) have a start, a middle and an end.

Time, Space and Culture Shock

A journey can be brief or extensive, or anything in between. The places you see can be familiar or exotic, near or far.

A trip to the local shop to get staples might be a 5-minute walk around the corner or up the street. You spend just long enough to do a common task in familiar surroundings and head back. This is the most basic journey; familiar and short.
You might drive across town to visit a close friend or family. Again, you are in familiar surroundings, yet you travelled beyond your immediate neighbourhood. This still feels like a small and safe journey yet you may spend hours on your visit and be surprised by the changed traffic or weather conditions coming home. A tiny bit more complex journey than the first example.
Maybe you’ve chosen to visit someone out of town or in another state. You might be invited to stay a few days. Longer distance means a little less familiarity: you don’t know the roads so well, where the post office is, the bed feels a bit different, etc. After a day or two, you start to get used to this. The longer you’re there, the more it feels like home.
While you’re there, you might take mini trips within the journey- go to the shop, the beach, maybe even camping out.
If you stay away long enough, when you come home it feels a bit strange at first. You almost turn the door key the wrong way, the colour of the wallpaper isn’t quite as you remembered it, you didn’t realise you were low on a few staples.
What if you set out on a grand adventure to visit strange and distant cultures? The journey is either massive, with strange and mysterious stops on the way, like an ocean journey, or super fast, almost like a blur, as in a flight. When you arrive, it’s almost alien. Everything’s different: the living conditions, the language, the food… Stay there for a while, however, and you gradually pick up a few basic words, learn a bit about the local neighbourhood and start to feel more settled.
Were you to stay in an exotic culture for long enough, it would start to feel like home, and your memories of your real home become less and less clear. Coming home after living there for years, home itself would feel like a very strange place at first. Stay somewhere long enough and you might even come home with a foreign accent!

All this can be mirrored in the way a piece of music progresses. The melody is the traveller, the main chords are the visiting points. Time is time.

The relationship between each chord and the home key (as well as between one chord and the next) is the relationship between home and the various places visited on our travels. As a (basic) chord represents a key, the main chords mark out the visiting keys in the journey.

Chord relationships are key relationships. A topic in itself, this is worthy of revisiting in at least one separate post. However, in general, keys (and chords) are related by how many notes they have in common. There are basically three types of key relationships:

The Cycle (or Circle) of 5ths

The cycle of 5ths is a sequence of all major and minor keys in increasing and decreasing key signature order, usually represented as a circle. Octaves are unspecified, as it’s just a list of keys. Adjacent keys in the cycle of 5ths have only one note different in their scales and both chords are made up of notes in the home key.

See my Beginner’s Tip for a graphic of the cycle of fifths, including relative majors/minors.

Adjacent keys in the cycle of 5ths are the closest companions. Many pieces only use 3 chords: that of the home key, previous key and the next key in the cycle, otherwise known as the Tonic, Subdominant and Dominant or I, IV and V. As we progress away from our neighbours, the keys sound less closely related and the chords a little more independent. Distant key relationships produce a startling or disorienting sensation in the listener.

Relative major and minor

All the common tonalities used in Western music have either a major 3rd or a minor 3rd from the root note. In this way, modes can be categorised as “like major” or “like minor” and be represented by a major or minor chord accordingly. It’s reasonable to talk in terms of major and minor chords, even if the piece is in another mode.

For every major scale, there is a minor scale with the same key signature (and vice versa). When the music changes between relative major and minor, the root note and tonality change but the notes all belong to the home key. As a chord progression, going from relative major to relative minor (and vice versa) feels more like taking a small step back rather than a significant change in key. Relative major/minor chords are often interchangeable in an accompaniment, depending on whether a more direct or a slightly indirect and more sophisticated effect is desired.

Major and minor on the same root note (parallel major and minor)

A major and a minor scale on the same root note have 3 notes that differ between them, so they only have 4 notes in common. In the cycle of 5ths that amounts to keys which are 3 steps apart, a relatively indirect relationship, yet they sound like they’re much more closely related. As it happens, only one of the three chord notes is different-the 3rd. The root note and 5th are both the same. The only thing that seems to change is the mood, the tonality.

Back to the present…

In short, closely related chords feel comfortable, almost predictable, as the melody arrives there – the friendly key next door…

Of course this is mitigated by the directness of the trip. We could potentially weave through a myriad of other keys before arriving next door, blindfolded and bedazzled, and it might then take us a while to realise where we are, but by and large, closely related keys can be freely visited in comfort.

More adventurous journeys use less direct key relationships or follow a cascading progression of keys in the cycle of 5ths to arrive in a new land.

When listening to a piece, try to feel not just the more rapid flow of the melody, but the deeper, underlying flow of the progression of keys through which the melody travels.

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