A long, long time ago music sounded very different to how it sounds today. Melodies were composed using a selection of scales called modes. These correspond to the white notes on the piano. C to C, D to D, E to E etc. Also melody was much more important than harmony. For your Medieval musician, playing a melody against a drone was the height of sophistication in harmonic accompaniment!

You may have spotted that C to C on the keyboard, which was called Ionian mode, is the same as our C major scale. As the Renaissance period progressed (circa 1450-1600 and the period before the Baroque) composers noticed the very strong progression created by chord V (dominant) and chord I (tonic) in Ionian mode. They eventually realised that you could create new dominant chords that would take you to a new degree of the scale and on this you could build a new version of Ionian – the major scale. Thus was tonality invented and with it, the concept of modulation.

Will Yow Walke the Woods soe Wylde by English composer William Byrd (c.1539/40 or 1543 – 1623) is a good example to show how this process of change started. Let’s listen to it.

We cannot call this music tonal. It is clearly modal (the strange sounding Lydian mode, in fact). But it does change its “tonal centre” up and down by one tone. Even “tonal centre” is the wrong way to describe this transformation (since it is not yet quite tonality and it sounds quite clunky). Musicologists say that the music has changed levels. The important thing is that you can see how Byrd is trying to break free of the restrictions of the modal system.

One of the most popular modes was that from A to A. (This was called Aeolian mode). The problem with Aeolian is that, like several other modes, it has a whole tone step between the seventh and eighth degrees. This means that it has no leading note. Instead it has a subtonic (G natural).

If we build a triad on the fifth degree of this scale/mode it gives us a minor triad. In order to create that highly confirming V-I feeling that Ionian mode possesses, composers started raising the seventh degree to accommodate a major dominant chord.

Now we have a new scale with a curious sounding top half.

This became the harmonic minor scale as we now know it. If you don’t like the somewhat exotic sound of the augmented second between F natural and G sharp, then composers had another solution. The melodic minor scale. In this scale both the sixth and seventh degrees of Aeolian are raised to copy the major scale or Ionian mode – but only when ascending! Descending they resort to the natural setting of Aeolian.

The problem was that at first, composers would let the ascending and descending versions of this scale happen at the same time. This would create quite alarming dissonances. You will find this quite a lot in music from around 1600.

Well that’s probably far too much information but hopefully you can see how we now have two types of tonality – Major and Minor, and that by creating new dominant chords we can modulate from one tonal centre (or key) to another. This is the essence of the tonal system we know today.

Major and Minor - Relative Keys

The smallest interval in western music is the semitone and there are twelve semitones in an octave. It follows that there are twelve major keys and twelve minor keys. Pairs of major and minor keys share the same key signatures – a relationship known as relative major and relative minor.

Each minor key is the sixth degree of its relative major key.

Each minor key is the three semitones below its relative major key.

Each major key is the third degree of its relative minor key.

Each major key is the three semitones above its relative minor key.

As you go through the major and minor keys in the table above, notice how with each added sharp you have gone up a perfect fifth on the keyboard. An easier way to look at this is by using the circle of fifths.

The Circle of Fifths

The circle of fifths is the arrangement of keys according to the number of sharps or flats in the key signature.

This arrangement is governed by the interval of a (perfect) fifth. If you travel up the keyboard in fifths you will visit each key in turn until you eventually reach the original key. The number of sharps and flats AND their order are also governed by the circle of fifths.

Here’s a mnemonic to help you remember the order of sharps.

Father Charles Goes Down And Ends Battle

Here’s a mnemonic to help you remember the order of flats.

Battle Ends And Down Goes Charles’ Father