I was playing on my clarinet the song Memory from the musical, Cats. It is written in 12/8 time. Although I know what that means -- the equivilent of 12 eight notes in a bar, I don't understand how it affects the rhythm. Would I play it differently if it were 4/4 time?
Yes. Is there a difference between 2/4 and 4/4 explains this using 2/4 and 4/4. However, this is a little different because it is compound meter. 12/8 has four beats divided into three equal parts. It would be counted like this:
The primary accent is on the first beat, the secondary accent is on the seventh, and there are two subordinate accents on beats four and ten.
4/4 would be completely different because it is simple meter.
There are four beats with accents on the first and third. If Memory was arranged in 4/4 time, it would most likely be arranged in triplets (one set per beat). This would naturally change the accents to fall on the (original) first and seventh beats with the fourth and tenth being almost non-accented. Also, if played at the same tempo as the original, the beats' duration would be a third of the original.
This would give the piece a completely different feel assuming the conductor interprets it correctly.
There's a tricky subtlety in time signatures like 12/8, but I'll do my best to explain!
Unless it's in with some odd time signatures, 12/8 can be split up in a few ways if we disregard feel that I'll explore here, all having 12 8th notes (bear with me, there multiple parts to this answer)
note that in the above 2 options, the stresses fall in weird places, out of sync with the words. The song sounds very odd if the words you put stress on are "A" and "In"(though it does sound pretty funny). now for the difference between 6/8 and 12/8, which is more subtle
In Compound times like 6/8 and 12/8 we think of the beats in threes. 6/8 is 2 groups of 3 quavers/eighth notes or - 1 and a 2 and a. 12/8 is 4 groups of 3 quavers/eighth notes or - 1 and a 2 and a 3 and a 4 and a.
I know what you may be thinking, 12/8 is just 2 lots of 6/8. At least that's how I thought about them for a long time! look again at the stresses in bold that I've mentioned above. the first one in each group is the 1st beat of the bar and the strongest. the second is also a strong beat of the bar, but slightly weaker than the first. In 4/4 This is the same thing the 1 and 3 in 1 2 3 4|1 2 3 4.
So now if we apply this heavy handed explanation of mine to the words, in 6/8 you would have:
mem - - ry - -| - All A Lone in the|Moon - - Light- - -| - - - - - -
and in 12/8 you would have:
mem - - ry - - - All A Lone in the|Moon - - Light- - - - - - - - -
The difference is, that in 12/8 your stresses happen less often, here giving the music a softer quality. If you try emphasising on the bold syllables you'll find that the 12/8 stresses flow far more naturally than the 6/8 stresses do.
To take it one step further, perhaps into speculation, the Strongest first beat in 12/8 falls on the syllables Mem, and moon which are also the two longest held notes in the music. In 6/8, they would also fall on Lone and Light which are intended to be shorter passing notes rather than spotlights. From a lyrical perspective, lone and light are the weaker/less important ideas in the bar, so you put them on the weaker beats and make them shorter to give way for the stronger ideas. Then the strong ideas get more space(in this case a dotted crotchet of more space!)
I hope that wasn't too ott of an answer, great question!
There is, in my opinion, and those of seasoned musicians I've discussed this with, no difference between the two as far as emphasis is concerned. Every tune will have its own 'feel' rhythmically, and apart from the 'standard' - beat no. one is usually the most important/ emphasised beat,12/8 is just a version of 4/4 with a triplet feel.
Often swing tunes are written out in 4/4 with the instruction at the head stating a triplet feel has to happen. If 12/8 was different, then why would they be written in 4/4 ? Probably to make life easier for both the writer and the reader.
Every muso. will have played tunes in,say, 4/4 that differed in the feel from one to another.Reggae, for example, is 4/4, but the feel is rather different from most other 4/4 tunes.
My answer may not be technically correct, but as far as practical playing and performance is concerned, there we are. Isn't that what this site is about ?
OK, first lets address the most basic part of your question - There is a mathematical difference between 4/4 and 12/8. So no you cannot treat it as 4/4. You could treat it as 3/2, but I'll get to that in a bit. I'm thinking (hoping) you actually know this but mis-communicated.
For those who don't understand the math of music, the time signature is basically a fraction to show how many whole notes are in a measure. You can do some division to reduce a time signature to it's most basic elements. So 4/4 can be reduced to 1/1 (i.e. 1) which means one whole note per measure. 3/4 means 3/4ths of a whole note, 1.5 half notes (a dotted half note), or three quarter notes in one measure. 12/8, means 12 eighth notes, or six quarter notes, 3 half notes or 1.5 whole notes (dotted whole) in a measure.
As for the stylistic interpretation - the main reasons for leaving an "unreduced" fraction as the time signature are:
Arguments about emphasis are completely false. 6/8 is commonly conducted in either 2 or 6 major beats and can be conducted in 1 or 3 also. Even 4/4 often has the highest emphasis on 1 and secondary emphasis on 3, but can be 4 equal beats. Really the style of emphasis should not be interpreted from the time signature. If not spelled out in accents, that is usually divined from the style (march, waltz, etc.) and other artistic interpretation elements.
Meter has to do only with measurement. 8th note triplets in 4/4 time is identical metrically to 12/8 meter.
How you play the notes is a matter of context, preference or convention. There are many concurrent factors that can influence this.