Anyone got a definitive (or convincing will do) answer to this one?

Started grade 2 theory with an adult student and we have got to time signatures like 2/2 3/8.
Had a bit of a problem coming up with a reason why composers might use these instead of keeping to crotchet as 1 count?
As she said, if is sounds the same why write it differently?
I pointed out that using a minim beat avoids all those small value notes in a fast piece (cosmetic?). but then a minim beat is also often used in a slow piece (giving a more spacious look).
Any advances on my dodgy ideas are welcome.

Why don't you dig out lots of pieces with different time signatures in and see how they look and play?

Sometimes I think time signatures are a bit arbitrary, and that on occasion a composer could just as well have picked a different one and it would make no difference at all in the way a piece is played.

Perhaps we should stop looking on composers with quite such reverence and see them more as the flawed individuals they really were, rather than infallible gods!

Violinia

I suppose 3/8 has a faster feel than 3/4, just because it's quavers.

The time signature might also relate to the previous movement's time signature in a sonata - 2/4 then 3/8, 4/4 then 3/4 perhaps. It might make a difference to how a performer would expect the speeds and musical flow to relate between movements.

I guess there are issues to do with how the printed music is perceived - how you would expect a piece that looks like that to sound - the speed, division of the bar, full of black beams or spaciously without beams etc.

There is of course an important distinction between time signatures that are in 2 time and those that are in 4 time. This makes a difference to the weighting of the beats in the bar, and as to whether it trips along in two big beats, or more in four. (4: 4/4, 4/8, 12/8.........2: 2/2, 2/4, 6/8.)

2: Strong, Weak.
4: Strong, Weak, Moderate, Weak.

-

i think its a sign of changing tempo.i mean the speed .

This isn't really relevent, but I find 3/4 really difficult, particularly to sightread, and yet I have no problem with 3/8. So perhaps its slightly deeper than purely cosmetic, or maybe it is cosmetic, and I simply find 3/8 makes the intended rhythms more obvious...

Odd as it may sound I find exactly the same thing 3/8 is so much easier to read than 3/4 even though it says the same thing!

I think it's just a matter of personal taste for the composers, maybe it started as some sort of indication of the speed but now it's just what the composer likes. Just in the same way we have different words that mean the same thing in the same language (othewise known as synonyms), perhaps that analogy would help the student to accept it although it's clearly not a proper explanation.