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Newb here. Learning time signature for the first time. Learning from online sources.


I've learned that the top number in the time signature is the the number of beats in the measure and the bottom number is the length of note that equals a beat.

I'm looking at an example measure that's in 6/8 time (see image below). The example says that 6/8 is compound duple. Duple is supposed to mean that there are 2 beats in a measure and compound is supposed to mean that each beat can be divided into three.

This doesn't make sense to me... we're supposed to have 6 beats in the measure because the top number is 6. If the top number signified notes instead of beats then 6/8 being compound duple could make sense — in this case there would be 6 notes in the measure, each note equaling an eighth note. Then, we could have a compound duple because we could make 2 beats for the measure, each beat being a dotted quarter note (which gives us two groupings of 3 eighth notes each). But I don't understand how we can have a duple (2 beats) when the 6 is supposed to indicate 6 beats.

Measure of 6/8 with six (un-beamed) eighth notes

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    The posted answers give more detail, but the short version is: What you've learned is correct, except that compound time is an exception because that's how people use it, so your next step is to learn this exception to what you've already learned :) Mar 24 at 18:34
  • Many of the answers here fail to mention that 6/8 doesn't have to be compound - I've had slow pieces conducted as literally just 6 quaver beats. But I think that's much less common than compound duple. Mar 26 at 9:24

6 Answers 6

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I've learned that the top number in the time signature is the the number of beats in the measure and the bottom number is the length of note that equals a beat.

That's half right. Top number is 'how many', bottom number is 'what of'. And in 'simple time' we can read this directly as the number of beats - 4/4 has 4 quarter note beats in each bar, 2/4 has 2.

But when the top number is 6, 9 or 12 we're in a 'compound time' where a beat consists of three 'pulses'. 6/8 adds up to six 8th note pulses, grouped as two beats. 9/8 has three beats.

Then there's 'irregular time' like 5/8. That just MIGHT be counted as five 8th note beats. But it's much more likely to be two beats, of different lengths.

And what's 'one-in-a-bar' 3/4 or 3/8? Three 'simple' beats or one 'compound' beat? Some people don't like the idea of 'compound single'. But they still beat a fast waltz or an Irish jig 'in one'. It can get complicated!

Some people think it would be clearer to write time signatures using the beat count and a note, like this. They have a point.

A measure in 3/4 (with the time signature written as a "3" over a "quarter note symbol") with three quarter notes.  A measure of 6/8 (with the time signature written as a "2" over a "dotted quarter note symbol") with three beamed eighth notes and a dotted quarter note.

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    "Some people" are wrong. That's hell for a sight-reader.
    – OrangeDog
    Mar 25 at 17:45
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    @OrangeDog That metric system is Carl Orff's! If you ever sing Carmina Burana, I have no doubt that your mind will be changed - you rapidly adjust, and then you discover how much simpler Carl Orff's system is than the "normal" system. Among other things, it really DOES let the number on the top of the time signature tell you how many beats are in a measure - no compound confusions. It also allows you to simply express meters that are very difficult to express in conventional notation. Once you adjust, it's a joy.
    – Ben I.
    Mar 26 at 1:16
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    @BenI. I've never had any compound confusion. The conductor decides how many beats there are. I just need to rapidly be able to read the notes and their lengths. I'm also used to singing old choral music that doesn't have time signatures at all, and the bars just separate phrases.
    – OrangeDog
    Mar 26 at 10:18
  • It looks like there's an A at the beginning of the measures—that seems unsightreadable.
    – Someone
    Mar 27 at 13:19
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This is a slight confusion of terminology that happens all the time when teaching/learning about time signatures.


The statement:

the top number in the time signature is the the number of beats in the measure and the bottom number is the length of [a] note that equals a beat.

…is correct for simple time signatures (such as 2/4, 3/4, and 4/4), but it is incorrect for (or at least a confusing way to think about) compound time signatures (such as 6/8, 9/8, and 12/8).

The way I learnt it, for compound time signatures, the top number indicates the number of pulses (not beats), where each beat is made up of three pulses.

So for 6/8 (which is compound duple) there are two beats that are dotted quarter notes, with each beat breaking down into three eighth note pulses.

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It is a widespread myth that there are 6 beats in 6/8 time. 6/8 time is indeed two time or duple time. Two beats with a beat being equal to a dotted crotchet. That is what compound time signatures are, a time signature where the beats are equal to note values with dots.

6/8 time is related to 2/4 time, the only difference being that 6/8 the beat has a dot, while in 2/4 the beat does not.

Time signatures are not that complicated. There are two, three, four-time. With beats of quavers, crotchets and minims, and beats with and without dots.

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    Sometimes there are six beats in a 6/8 measure. It depends on the tempo.
    – phoog
    Mar 24 at 18:29
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Time signatures have a complicated history. However, the current practice is fairly consistent, though not obvious. Measures and bar lines are primarily used to make music easy to read; the time signatures and bar lines follow the music; the music isn't a slave to the bars.

Time signatures are not fractions; they are just symbols used conventionally. The bottom number gives the type of note being (nominally) counted. For example, 3/4 or 4/4 mean count by quarter notes; 6/8 by eighth notes, and 3/16 by sixteenth notes, etc.

The top number gives the number of notes in a measure: 2/4 means 2 quarter notes; 3/2 means 3 half notes, 9/16 means 9 sixteenth notes, etc. There are a few conventions about the top number's meaning. The numbers 2, 3, or 4, mean the pulse is the same as the bottom number's note. In most styles of music, there is an implied accent on the first note of the measure. A top number of 4 means a secondary accent on the third pulse. Of course, the actual music may not follow these conventions (by using phrasing and beaming to override the convention.)

Except for the number 3, the top note's divisibility by 3 indicates a compound measure. (It's a shortcut to avoid writing too many triplets.) A signature of 6/8 means the feel or pulse is two eighth note triplets; 6/4 is two quarter note triplets (note 4+2. I like to think of these compound measures as "long" measures: 6/8 as 3/8+3/8, 9/8 as 3/8+3/8+3/8; this goes well with odd measures like 7/4 being 3/4+4/4 or 4/4+3/4, etc.

A bit of history: time signatures (like key signatures) carried more types of meaning. A circle was 3-beats (tempo perfecto or something like that). A broken circle was 4 beats which became C or 4/4 (or "common time" to match the C). After metronome markings became common, 3/8 and 3/4 became essentially the same, and the duration of the pulse was given by the metronome marking. The time values of note symbols (quarter, eighth, etc.) became more flexible.

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  • The broken circle was two beats, not 4; there was also note value inflation.
    – phoog
    Mar 24 at 18:31
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    That's correct. The broken circle became common time through more changes. There are a bunch of old time signatures that are not used but also contain tempo information. The history is interesting. The current conventions are easier to use. The only problem is the unwritten performance implications. (Military marches and some French Overtures being double-dotted, swing implied on eighth notes but not quarters in some styles, several dance styles writing 4/4 but meaning (3+3+2)/8, and others.
    – ttw
    Mar 25 at 3:08
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I've learned that the top number in the time signature is the the number of beats in the measure and the bottom number is the length of note that equals a beat.

Everybody learns that! It's more or less true but it's also an example of a lie told to children. I mean this quite literally; I believe I was 7 when I first encountered it.

A better explanation might be that the upper number tells you how many time units are in each measure; the lower identifies the units of which you will find that many in a measure.

How many seven year olds do you know who can understand abstract concepts such as "time units"? Add to this the fact that most beginning music students aren't yet playing pieces in 6/8 that are fast enough to be counted in two, and the utility of the given explanation is clear.

The number of beats per measure depends in part on the tempo, and there is a range of tempos within which reasonable people will reasonably disagree about whether, for example, a measure of 4/4 should actually be counted in 2.

The ambiguity is much more common with compound meters, and you will also find more compound meters that are unambiguously on one side or the other of the question. You will also find this with simple triple meters: 3/4 is often intended to be "in one," and Beethoven is well known to have organized different parts of his ninth symphony, nominally in 3/4 but so fast that it must be in one beat per measure, into "supermeasures" of either 3 or 4 bars, using the phrases "ritmo di tre battute" and "ritmo di quattro battute."

One reason for this ambiguity about which unit of time corresponds to the "beat" is that time signatures began their lives as fractions expressing a proportional relationship (see mensural notation if you're interested). Once the modern meaning arose, various conventions and common practices were already well established, and there was no wholesale redesign of the system.

The older system had an ambiguity whereby each level of note duration could be subdivided into two or three parts, depending on the context, based on certain rules. When the rules nonetheless left it ambiguous as to whether a whole note, for example, was to have the duration of two or three half notes, the convention arose of using a dot to indicate that it was three half notes. This was the "dot of perfection," since the triple subdivision was considered "perfect" and the duple subdivision "imperfect."

The dot of perfection led to the modern dot, the dot of augmentation, and the rules for sometimes subdividing into two or three fell by the wayside. This led to the current situation: if you want to write a piece with a two-beat meter and a triple subdivision, you can either write a triplet indication over each beat or write the piece in 6/8 (or 6/4 or what have you).

Sometimes, in modern scores, you might see the bottom number of a compound meter replaced by a dotted quarter note (or dotted half note, or what have you), but this practice is far from universal.

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Compound duple has always been the most difficult to explain (for me!) and also to understand (for you and many others!)

6/8 can be counted in both ways, 123456, and 1&&2&&. That in itself isn't enough explanation.

There are 6 quavers in a bar for 6/8, but there are the same 6 in 3/4. That's where the complications arise. In 3/4, the count is 1&2&3&. One emphasis in a bar. Whereas in 6/8, there are 2 emphases - on 1, and half way through the bar.

There needs to be a way to differentiate between the two time signatures, which both, mathematically, equate to the same. Hence 3/4 for the simple 3 crotchets per bar, and 6/8 for the more complicated - compound - timing.

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