Distinguishing time signatures

[moley]

Originally posted by Rick Blanc
I thought the bottom number describes which note gets one beat. I.E. In 3/4 time a quarter note gets one beat. In 6/8 time an eight note gets one beat. I could be wrong though.

Yes, you're right, but it's not quite as simple as that with compound time. 6/8 designates 6 8th notes in one bar - but the *main* beat isn't an 8th note, it's a dotted quarter. Not entirely logical, you could say - but that's just the way it's done, so I guess you just have to know it.

 

[Howard K]

aah, i see!
...that was what was confusing me a little about your description of compound time in relation to 6/8.
i understood what you were saying, but i had saw a conflict there, so i'd just assumed it was "one of those things that just are"!

 

[wulf]

Originally posted by Rick Blanc
I thought the bottom number describes which note gets one beat. I.E. In 3/4 time a quarter note gets one beat. In 6/8 time an eight note gets one beat. I could be wrong though.

Not necessarily - that, I believe, is why compound time is given that name... eg. 6/8 feels like two beats, each subdivided into three (see moley's post, some way above).

Out of interest, would playing a piece in 2/4 and using eight note triplets in one bar be functionally equivalent to playing in 2/4 but inserting a bar of 6/8? Or would a bar of 6/8 last as long as 1.5 bars of 2/4 (without additional notation of a time change)? I assume the latter is the case, but would be interested on what others think.

Wulf

 

[moley]

Originally posted by wulf
Out of interest, would playing a piece in 2/4 and using eight note triplets in one bar be functionally equivalent to playing in 2/4 but inserting a bar of 6/8? Or would a bar of 6/8 last as long as 1.5 bars of 2/4 (without additional notation of a time change)? I assume the latter is the case, but would be interested on what others think.

Ahh, well it depends. Generally, when there is a time sig change like that, you need to specify which note value stays constant. It could be either way.

Above the stave you might see something like eigth = eigth (but with eigth notes instead of the word 'eigth'). That would indicate that the length of an 8th note stays constant - which would mean that the 6/8 bar would be as long as 1.5 2/4 bars. However, you could see quarter = dotted quarter (again, notes, not words) - and that (I think, but that could be the wrong way round, it could be dotted quarter = quarter, I forget) would indicate a quarter in 2/4 is equivalent to a dotted quarter in 6/8. That would mean that the main beat stays constant, but it goes from being divided into 2s to being divided into 3s. Like going from a straight feel to a swing feel.

 

[Pacman]

Originally posted by Rick Blanc
I thought the bottom number describes which note gets one beat. I.E. In 3/4 time a quarter note gets one beat. In 6/8 time an eight note gets one beat. I could be wrong though.

That's true to a degree, but that's what gets us compound time to begin with. 6/8 for example is compound duple, or two beats divided into three parts each. That means the dotted quarter gets one beat, and there's no number for dotted quarter. So in compound time, the bottom number is the divided beat. See?