Counterpoint

Another explainable music phenomenon

Before diving into this it would be helpful for you to read my basic music theory post and possibly more music theory.

Counterpoint is often described vaguely as ‘two voices playing off each other’. There are different phenomena which are referred to as counterpoint, but they all have two things in common: There’s more than one melodic line, and they aren’t playing in parallel. The most basic form of this is caused by an internal contradiction within the diatonic scale, best illustrated by labelling every other key like so:

You might notice that the white and yellow keys each form their own nice sub-scales where every pair of adjacent notes is a (major or minor) third apart and with one exception every pair notes two apart forms a fifth. This make the scale have similar properties to the pentatonic in that you can bang on notes roughly at random and it will all sound consonant, but it has two weaknesses: It has even fewer notes per scale than the pentatonic at 3.5 per octave, and it doesn’t contain the octave, which is the strongest consonance on the piano. To illustrate this the C notes above have been given asterisks, and you can see they alternate between white and yellow. This is because there are seven notes in the octave and seven is an odd number. In case you’re wondering why it’s called an ‘octave’ which indicates eight that’s because the vernacular predates people believing zero was a real number so all the interval names are off by one.

The result of the above is that a lot of melodic lines clash if they’re played in parallel with another instrument one octave off. If they’re two octaves off it returns to the same half-scale and it’s safe to play in parallel again. When there are two instruments about an octave apart they tend to dance around each other, playing in the same half-scale or hitting the octave on the off-beat or otherwise doing whatever they can to avoid playing a second against the other other instrument when one of them hits a seventh. This dancing around is referred to as ‘counterpoint’.

This phenomenon doesn’t apply to the pentatonic scale where it’s always consonant to play the same melodic line in parallel an octave apart.