Session 3: What key are we in?

What does “the key” of music mean?

Often as not when musicians get together to play you’ll hear the question: “What key is this music in?” But even when you know the answer, what does it actually mean?

The key of the music isn’t necessarily the first chord you play. “The first chord is A minor, so we must be in A minor. Right?” Wrong! You might be in A minor, but there’s no certainty about it.

Try playing these chords in order:


Or listen to them by clicking on the play button below:

When the G chord comes there’s a clear sense of arrival, of being home. G is the “home” chord. We’re in the key of G major – even though G wasn’t the first chord. (Don’t forget that calling the chord “G” is actually a form of shorthand; the full name of the chord is  “G major” – that’s implied when you see the letter name by itself. And that’s why the key is called G major, though again it’s often simply implied: “OK guys, we’re doing Baa Baa Black Sheep – in G”.)

In most music there’s one specific note or chord like this that gives the sense of being “home”. When you’re away from it you feel a tension. Returning to it feels like arriving back at base. That note or chord is the “key centre”.

Here’s an example in a minor key:


Here the A minor chord feels like the destination we were heading for. It’s our “home” chord, and the key is A minor.

Some short pieces of music may just stay centred around one base – in other words they stay in the same key throughout. But it’s common for pieces of music to add variety and interest by having sections that are in a different key for a while before coming back to the home key.

Some music even starts in a different key before establishing home (good examples are Beethoven’s 1st symphony and Jimi Hendrix’s song “Angel”). The music might even end in a new and different key if the composer wants to create a particular effect, but that’s unusual on shorter pieces (and even on longer ones). Generally, if the music is mostly in say A major but some sections are in a different key you would describe the whole piece as being in A major. And the pull of the key centre is so strong that the music comes back to it by the end. The home key is like the sun with its massive gravity. All the music seems to revolve around it and get swept up by it.

Why you need to know what key you’re in

Organising music around a key centre – what’s called the principle of tonality – is so much a part of Western music and feels so natural that you can play and even write music without being particularly aware of it, in the same way that a child can learn to speak without consciously studying grammar and vocabulary. But if you want to understand how music works, to develop your ability to work with it, to hone your craft, it’s essential knowledge. A child can get away without knowing about grammar, but if you want to be involved with writing in a serious way you need to dig in deep and get to grips with it. It’s the same with music –  you’re going to remain at a very simplistic level if you don’t understand the basic materials you’re working with.

At the very least, if you play music that’s entirely written (e.g. for classical guitar) knowing the key means that you know which notes to sharpen or flatten.

If you play music that’s not written down you need to know the key. Knowing the key tells you which chords and notes will work well together. You get familiar with the way they sound, so it tells you what chords and notes you’re hearing in your head before you play them. It tells you how to use more distantly related chords and notes. Without this you’re shooting in the dark.

Do you compose music? Being aware of the key opens those same possibilities for developing your ideas. What are the chords and notes that the listener will be expecting? How can I meet or upset those expectations? If you’ve ever felt stuck on the same few chords and don’t know how to progress you’ll see how useful that is. It’s like a roadmap – you don’t have to follow any particular route but at least you’ll be aware of the options.

And though it’s less immediately obvious there’s also a deep connection between tonality – the use of key centres – and the structure or form of music. Extended pieces use the principle of tonality to differentiate one section of music from another. For example a typical classical sonata movement will have a group of themes in the home key, followed by a group of themes in a related but different key. It will then move through a range of more or less related keys before settling back and playing all the themes in the home key. It’s a real journey, using the different key centres to help give a sense of direction.

The next session looks at the notes in major keys, and how the key defines which notes need to be natural, sharp or flat. Or – another way of saying the same thing – how the choice of notes defines the key.

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