Two time signatures at the same time.

[mjames]

Okay, what?! So I was reading the score to profokiev's second concerto and the first thing i noticed were the two time signatures. 4/4, and 12/8


Okay, now someone's got to explain this to me. How does this work?

[j_menz]

You know what 4/4 is. You know what 12/8 is. You know what a polyrhythm is. This is just a special case of one.

Unless it's written 4/4 12/8 on both staves at the start, in which case you alternate between them (it should be obvious from the score which is which).

[brogers70]

In Janacek's "They Chattered Like Sparrows" there's a section which is 5/8 in the right hand and 4/8 in the left. You play it as a polyrhythm so that the first beats of each measure coincide. The 12/8 versus 4/4 might be pretty simple - 12/8 is like 4/4 with triplet eighths, so lining things up shouldn't be too hard.

[mjames]

oh okay, so *scratches head*

You play the eight notes in 12/8 as triplets so they can line up against the 4/4?

[brogers70]

oh okay, so *scratches head*

You play the eight notes in 12/8 as triplets so they can line up against the 4/4?

I believe that is correct, yes.

[j_menz]

oh okay, so *scratches head*

You play the eight notes in 12/8 as triplets so they can line up against the 4/4?

In this case, yes. 12/8 is compound time, so naturally falls into four groups of three. Each group of three corresponds to a single crotchet in the 4/4 bar. So, it's a basic polyrhythms. It also makes one wonder why Prok bothered to notate it as such - other composers would have just gone 4/4 and taken it as read - and shows him to be rather more pedantic than I'd have thought (though I don't play much by him, so perhaps shouldn't be surprised).

[mjames]

In this case, yes. 12/8 is compound time, so naturally falls into four groups of three. Each group of three corresponds to a single crotchet in the 4/4 bar. So, it's a basic polyrhythms. It also makes one wonder why Prok bothered to notate it as such - other composers would have just gone 4/4 and taken it as read - and shows him to be rather more pedantic than I'd have thought (though I don't play much by him, so perhaps shouldn't be surprised).

That's what made my head burn so much. I was like "why didn't he just write it in 4/4?" But yeah thanks, that clears things up a bit.

[brogers70]

The only reason I can think of for notating it that way is this. 4/4 is sort of a "squarish" rhythm, while 12/8 has more of a lilt to it, so he may be aiming for a slightly different feel in the two hands.