17. Time signatures

In the last episode we talked about the different lengths notes can have, which is a way to divide time in sensible lengths, so we can combine them to create rhythms.
Then bars are like containers in which we put these notes. And these bars are a good way to divide a song as well. Especially because bars can be of different lengths, so they don't always contain the same number of beats.

The way we tell how many beats fit in a bar is called a time signature. It appears in the form of two numbers at the beginning of a bar. The top number tells how many notes fit in the bar, and the number below it tells the nature of these notes. Most of the time it's a quarter note or 8th note.

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Then all the bars after that would be of the same size until another time signature appears and tells otherwise.

So a signature of 4/4 tells us that the bar is made of 4 quarter notes, so it's 4 beats long. This is the most common time signature in today's musics. So common that it's sometimes written C instead of 4/4.

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But unlike some may think, this C doesn't stand for "common", as this signature hasn't always been the most used. And It all comes back from the middle age.

LITTLE DETOUR TO THE MIDDLE AGE

Back in the middle age, around the XIIIth century, in Europe, the concept of bars didn't really exist. Though at this time we already had some symbols to write notes of different lengths. But the relative lengths these notes could vary.

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Long story short, in the XIVth century, the breve (which is like the longest note) could be divided in either 2 or 3 subdivisions.

If it was divided in 3 subdivisions, it was said that the tempus was perfect. And the tempus was imperfect if the breve was divided in 2 subdivisions.

(The 3 subdivision being the perfect one is apparently linked to the veneration of the holy trinity as most of these musics at the time were written for the church.)

Then these subdivisions of the breve, called the semi breve could also be divided in 2 or 3 subdivisions. In this case we talked about major prolatio for 3 subdivisions and minor prolatio for 2 subdivisions.

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So you had these 4 possibilities:
the tempus perfectus, where the beat is divided in 3, was indicated at the begining of the score by a circle.
And the tempus imperfectus, where the beat is divided in 2, was indicated by a half circle.

Then if the prolatio was major, a dot was added in the circle or half circle.
And this is were the C comes from. Originally It's not a C, it is a half circle that means "tempus imperfectus prolatio minor", in which every beat is divided in 2 subdivisions that are also divided in 2 subdivisions. Just like our 4/4 that became the most used time signature.

This is a very short version of how it worked back then. Maybe someday I'll make an episode on how European music evolved in this part of the middle age, and how France kinda rocked the game in term of innovation at that time, but for now, there you go.

COMING BACK FROM THE MIDDLE AGE

Now let's have a look some different time signatures

We already talked about the 4/4 where a bar is made of 4 beats. Usually the first and the third beats are considered strong beats, with the first one being the strongest. So the beats 2 and 4 are considered weak beats.

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As a basic drum pattern to highlight that, we often find a kick drum on the first beat and a snare on either the 2 and 4, or on the 3rd beat

With a time signature of 3/4, the bar would be filled with 3 quarter notes. So the bar would be made of 3 beats, with the strong beat being on the 1, and the beats 2 and 3 being weak beats.

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A bar with a time signature of 6/8 would also be 3 beats long, because that would be six 8th notes. So that's the same length than three quarter notes.
But the 8 as a denominator is a hint that the strong and weak beats cannot be divided in quarter notes. In fact in a 6/8 the strong beats would be on the first and fourth 8th notes, the first one being the strongest. So it's like a 2 beat bar with each beat divided in 3 subdivisions.

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The 4/4 and 3/4 are called simple time signatures. It means that the beat is divided into simple notes. Here the beat falls on every quarter notes.
The 6/8 however is called a compound time signature, because the beat is divided into dotted notes. Here the beat hits every dotted quarter notes.

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Another example of a compound time signature can be the 9/8. Here, the bar contains nine 8th notes. A common way to divide that bar would be to put the strong beats on the 1st, the 4th and the 7th notes.

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There with all these time signatures we covered the equivalent of all the tempus from the XIVth century we saw earlier.

The 4/4 would be the equivalent of the tempus imperfectus prolatio minor, where long notes are divided in two, and the subdivisions are also divided by two.

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The 3/4 would be the equivalent of the tempus perfectus prolatio minor, where long notes are divided in 3, and the subdivisions are divided in two.

The 6/8 would be the equivalent of the tempus imperfectus prolatio maior, where long notes are divided in 2, and the subdivisions are divided in 3.

And finally, the 9/8, the least common of the 4, would be the equivalent of the tempus perfectus prolatio maior, where long notes are divided in 3, and the subdivisions are also divided in 3.

Among these 4, It's interesting to see the most used time division from the middle age become the least used time signature today.

But this modern time signature system allows us to create more types of time signatures, to make bars of 5 or 7 beats for example. 

ASYMETRIC METERS

This would make some time signatures like 5/4 and 7/4, or 5/8 and 7/8. These kind of time signatures are called asymmetric meters because they are not made of groupings of 2 or 3 notes, but a mixture between the two.

The 5/8 for instance can be counted either like a group of two 8th notes + a group of three, or a group of three 8th notes + a group two.

In the first case, the accents, or strong beats, would fall on the first and the third notes, and in the second case it will fall on the first and fourth notes.

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For a 5/4 bar, it would work in the exact same way, but with quarter notes instead of 8th notes.

For a time signature of 7/8, it would work with the same groupings of 2 or 3 notes. So it can be either 2 + 2 +3, or 2 + 3 + 2, or 3 + 2 + 2.

In the first, the strong beats would fall on the 1st, 3rd and 5th notes 
In the second, they would fall on the 1st, 3rd and 6th notes
And in the third, the accents would be on the 1st, 4th and 6th notes.

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For a 7/4 signature it would be the same but with quarter notes instead of 8th notes.

And it works in the exact same way with a time signature of 9/8 we just saw earlier. With groupings of 2 and 3 notes we can have all this different combinations.

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With all this, you could make your own time signatures with simple, compound or asymmetric meters. You can even use several of them in one song, as a song doesn't need to use only one time signature all the way, and each one have its own character and its own vibe.

Knowing how to identify where are the strong beats or accents should help you to get used to them. 
This being said don't hesitate to move these accents around, I'm giving them as guidelines but there are a lot of example of musics putting the accents on different beats.

But for now, we still haven't talked about polyrhythms and that's something I'd like to tackle in the next episode of this series.

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