Time Signatures

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Time signature

What is a time signature?

The most straightforward definition is that it tells you how many beats in the bar (bar is "measure" in some countries).

But what does that mean?

Primitive music includes a lot of untuned percussion, and it's the beat or the pulse as we sometimes call it, that defines the character of the music. A slow beat is relaxing. A fast beat is exciting.

But the grouping of the beats also defines something about the music - let's make some categories of music - it's not an exhaustive list, but it will get us started.

The bar lines show where each March, Waltz or Jig step recurs.

Why do we need a time signature?

Arguably the regular occurrence of bar lines is enough to show where the steps recur, but there is the matter of how notes are grouped inside each bar.

The format of the time signature

As with so many logical systems, there are some illogical warts on the smooth and clear surface, but let's deal with the basics...

It's the bottom number that lets the confusion well up, and it's the bottom number where the first illogical things start to happen.

Some posh words

Let's take a leaf out of my "Degrees of the scale" article and try to define our categories of beat using different words...

First, let's make a distinction between "Simple" - the steady feel or a March of Waltz - and "Compound" - the skip or jig-step which gives the music an underlying "long-short-long-short" feel.

So what is "Compound Triple"? It's rare, that's what it is! The Irish know it as a "slip-jig", but little famous music is in Compound Triple.

A simple beat is actually nothing more than a beat that breaks into two halves, four quarters or a mix thereof.

A compound beat, though, breaks into three equal units. Think of the word "evenly". A skip is a compound beat that is broken into a long piece (2 units) and a short piece (1 unit).

Some examples

2/2 is Simple Duple - take a march step every minim.

3/4 is Simple Triple - take a complete waltz step every bar.

4/4 is Simple Quadruple - any bar of 4/4 looks like a bar of 2/2 and vice versa (because 4 crotchets or their equivalent adds up to the same amount of music - a semibreve - as 2 minims or their equivalent), but 4/4 has four steps per bar and 2/2 has two steps.

A common misconception

A common misconception is that all time signatures with an 8 at the bottom are compound.
But no, the definition of a compound time is that the top number is divisible by 3.

It just so happens that the common signatures with an 8 underneath - the ones you nearly always see - are 6/8, 9/8 and 12/8

A table of the more usual time signatures

Signature Counting minims Counting crotchets Counting quavers
Simple Duple 2/2 2/4 -
Simple Triple 3/2 3/4 3/8
Simple Quadruple 4/2 4/4 4/8
Compound Duple - 6/4 6/8
Compound Triple - - 9/8
Compound Quadruple - - 12/8
Irregular virtually all others virtually all others virtually all others

Signatures marked "-" are not illegal, they are simply rare.

A point of confusion

So is 3/8 a waltz step (3 beats in the bar), or a jig step (1 compound beat in the bar)?

The distinction between jig and waltz is one of tempo. Usually a bar in 3/4 is slower than a bar in 3/8, but it is not always the case. So usually, 3/4 is the waltz and 3/8 the jig. But not always.

See also

The degrees of the scale article

The key signatures article

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