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17. Time signatures

Hi there it's Woochia and this is music theory in 5 minutes. In today's episode we'll talk about bars and 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. Bars are like containers in which we put these notes. And these bars are a good way to divide a song, so it's useful to make the structure of a song.
It's easier to say "the verse is 16 bars long" instead of "the verse is 64 beats long". 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. And 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 quarter notes or 8th notes. Then all the bars after that would of the same size until another signature appears and tell 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. 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

IN MIDDLE AGE

Back in the middle age, around the 13th century, in Europe, the concept of bars didn't really exist. Though at this time we already had different sombols to wright notes of different lengths. But the relative lengths these notes could vary.
Long story short, in the 14th century, the breve (which was kind of the equivalent of the quarter note) could be divided in either 2 or 3 subdivision. 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 linked to the veneration of the holy trinity as most of these musics at the time were written for the church.
Then these subdivisions, called the semi brèves 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.
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.

Now let's have a look some different time signatures

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.
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 of 3 beats, with the strong beat being on the 1, and the beats 2 and 3 being weak beats

A bar with a time signature of 6/8 would also be 3 beats long, but the 8 as a denominator is a hint that the strong ans weak beats cannot be divided in quarter notes. In fact in a 6/8 the strong beats would be on the first and 4th 8th notes, the first one being the strongest. So it's like a 2 beat bar with each beat divided in 3 subdivisions.
Here is what is sounds like compared to a 3/4 measure.

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.

Another example of a compound time signature can be the 9/8. Here the bar contains 9 8th notes, and the strong beats fall on the 1st, the 4th and the 7th notes. So it sound like this.

RELATION WITH MEDIEVAL MENSURAL NOTATIONS

There with all these time signatures we covered the equivalent of all the tempus from the 14th 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.

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 asymetric 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 2 8th notes + a group of 3, or a group of 3 8th notes + a group 2.
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 4th notes

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, 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

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

With all this, you could make your own time signatures with simple, compound or asymetric 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 on 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. Perhaps I'll even a video about that. 
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.
So if your liked this video of found it useful, hit the like button, subscribe to the channel if you don't want to miss the next one, and in the meantime, thanks for watching, and I'll see you next time!

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