How does one know the implied difference in time signatures? [duplicate]

Question

I have always been told that the difference between 3/4 time and 6/8 time is that 6/8 time has two beats per measure and 3/4 has three beats per measure.

However, other than people telling me this, I see no way that someone would be able to know this just by looking at the music.

For instance the following example seems like it should be played identically:

Is there any way to distinguish the difference between how 6/8 and 3/4 music should be played other than just somehow knowing that one usually has the emphasis on two beats in a measure and one on three beats per measure?

Similarly, with cut time and common time, is there anything identifiable (without listening to the song) that differentiates the time signatures?

Looking at the above, I would think:

2/2 means two half notes per measure, which can be divided to four quarter notes per measure, which could be reduced to eight eighth notes per measure, so we are still in 4/4.

I personally count quarter notes and eighth notes and 16th notes as (1 2 3 4) vs (1 + 2 + 3 + 4) vs (1 e + a 2 e + a...) respectively but unless someone were hearing me count while playing, how would he or she know that the piece is in 2/2 vs 4/4 vs 8/8?

When looking at the second image, I would think one of two things:

1. The bar line should be after the first four eigth notes (because that would be two beats) or
2. "Okay, I see 8 eighth notes. I am going to count each measure as "1 + 2 + 3 + 4 +" (because that is how I count eighth notes)"

but this would be wrong because I should only count up to 2 (two beats per measure) so instead I'll count (1 e + a 2 e + a) but this is also wrong because that would imply we are in 8/16 time.

So I do not see a valid way to count this. I would very appreciative if someone could explain this to me.

Answer 1

The answer to both questions is the same: it's understanding meter

Meter is the pattern of accented and unaccented beats. Both music and poetry have meter: RO-ses are RED has a pattern of one accent followed by two unaccented syllables; i WISH i KNEW how LONG has a pattern of one unaccented and one accented syllable.

In poetry there are lots of different meters with fancy names like dactyl (roses are red) or iamb (i WISH). In music they're simpler: we group beats into twos or threes, and we divide beats into twos or threes.

Grouping beats in twos is duple meter. 2/4 and 6/8 are both duple meters, with two beats per measure. Grouping in threes is triple meter, as in 3/4 or 3/8.

The way we divide the beats can be into two equal parts (one quarter note beat = two eighth note divisions), which is called simple meter, or we can divide beats into three equal parts (one dotted quarter beat = three eighth note divisions) which is called compound meter.

Meters are represented by the time signature. If the top number is a multiple of three (6,9,12,15) it's compound meter, and the bottom number is the type of note that represents a beat division, or one third of a beat. If the top number is anything else it's showing you a simple meter - then the bottom number tells you the type of note that represents one full beat.

Groups of beats can be combined: 4/4 is two groups of two beats. The first group's accent is slightly stronger than the second group's accent: ONE two THREE four, and because 4 is not a multiple of 3 each beat will naturally divide into two parts. We call this quadruple simple meter.

The time signatures you ask about are 3/4, which is a triple simple meter and 6/8, which is a duple compound meter. 3/4 has three beats per group with beat one accented, and each beat naturally divides into two parts; 6/8 has two beats per group, with each beat divided into three equal parts.

4/4 is quadruple simple, with two groups of two beats. 2/2 is duple simple, with one group of two beats. The difference here is subtle: the second group in 4/4 is accented a little less than the first group's. In 2/2 all accents are the same.

You didn't ask, but we can also combine unlike groups: 5/4 time is one group of three beats and one group of two. Meters like this are called asymmetric. For an asymmetric meter we don't know if it's grouped 3+2 or 2+3 - either will have the same time signature. For those we usually use the beams within divisions to tell the musician how the notes are grouped.

Answer 2

'I see no way that someone would be able to know this just by looking at the music.' The simple answer here is to look at the time signature.

3/4 and 6/8 look very different from each other! That's because they are! And playing your example would come out differently. The 6/8 tune would have an empahsis on the first note (like most music) but also on the fourth. That's implicit in the time signature. Very different from 3/4.

A point of order: there should not be six separate quavers written, they should be beamed. 3/4 can be as three pairs, 6/8 as two groups of three. That's how they get played - that's how they get written.

How do we know? By learning it. We learn that to, too and two, or you, yew and ewe all sound the same, but very quickly as kids realise that they are actually all different. So we learn in music that there are different ways in which to designate timings.

Answer 3

However, other than people telling me this, I see no way that someone would be able to know this just by looking at the music.

Of course! Musical notation is written language used by people in a culture. Did you learn to read text by looking at text, without actually speaking any language or meeting any speakers of any language?

It's about culture, conventions, tradition and language. Not natural science, laboratory measurements and math. If you ask yourself "should I write this in 3/4 or 6/8" and cannot tell the difference, then you lack cultural, not theoretical knowledge.

You can't calculate it, you need to get involved in the culture to understand it.

(Paraphrasing my own answer from here How does the bottom number of the time signature affect counting?)

Answer 4

1. Let's assume your problem is not the differentiation of the six 8th-notes in a 3/4 time compared with the six 8th-notes in 6/8. (3/4 you count 1 a 2 a 3 a, 6/8 time you will count 1 2 3 4 5 6.

2. I think the question is how to differentiate a 6/8 from to bars of3/4, isn't it?

The problem is actually that it isn't always clear even to the composer to decide which time signature is more adequate, as we have mostly motifs of a double bar or even 2 double bar phrases which would fit as well in a 6/8 time signature (I think I have also seen a Waltz notated in 6/8).

So if the 1st point is clear to you I wouldn't bother to much about the difference of these 2 kind of notations. It is not so much crucial as you may think.

Concerning the 1st point: I have written a long time ago a piano piece (polyrhythmic): l.h. 3/4, r.h. 6/8 and vice versa. In this case it is possible to mix the 2 rhythms resp. times, but the notation would be complicated. The solution is to notate the piece in 3/4 and add accents on 1 and 4 of the 6 8th notes. Note the Cello part in this arr. for Strings:

or the first bars for Piano: (unfortunately the software doesn't allow 2 different times in the upper and lower staff ...)

Answer 5

It's not an implied difference.

It's specified in the time signature.

You have to learn to read time signature. They are not self explanatory.

The tip off is in the top number. Basically, if it's a multiple of 3, and the bottom number is 8, then it's compound time and the beat is subdivided by three.

The problem with your example of eighth notes in 6/8 and 3/4 is that it is written poorly. Good rhythmic notation will put beam on eighth notes grouped into beats, 3 notes in 6/8 and 2 notes in 3/4.

Again, you need to read a book of music fundamentals about rhythm and time signatures to get the full picture.

Answer 6

Y0u are quite correct that, shown just this, we have no way of telling whether 2+2+2 (3/4) or 3+3 (6/8) grouping is required.

And that is why we have time signatures!

The 3/4 time signature tells us it's 2+2+2.

And, to make it even clearer, we'd normally write it like this.

For 3+3 we use a 6/8 time signature and this grouping.

Answer 7

One difference with compound time signatures is that instead of counting beats, we count pulses.
In compound time signatures there are three pulses to a beat, whereas in simple time signature there are only two.

This is represented as a clear visual difference by the beaming; we connect the flags of the pulses into beams, and we do this according to the beats.

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The compound duple time signature 6/8 says that there are 6 pulses to the bar and they are eighth notes (quavers). (As already mentioned) we count the pulses in compound time signatures.

Below is two bars in 6/8, the first showing beats, and the second showing pulses:

X: 1
K: C clef=perc stafflines=1
M: 6/8
L: 1/8
V:1 stem=up
B3 B3| BBB BBB||
w: ~1 ~4 ~1 ~2 ~3 ~4 ~5 ~6 

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The simple triple time signature 3/4 says: there are 3 beats to the bar, and they are quarter notes (crotchets). We count beats in simple time signatures.

Below is two bars in 3/4, again the first bar shows beats, and the second shows pulses:

X: 1
K: C clef=perc stafflines=1
M: 3/4
L: 1/4
V:1 stem=up
B B B| B/2B/2 B/2B/2 B/2B/2||
w: ~1 ~2 ~3 ~1 ~& ~2 ~& ~3 ~&