Special layout for a score : four hands

[Jean-Charles Malahieude]

Hi, all!

Some time ago, Werner asked on the devel-list in a thread about "setting 
the number of pages for a score"
http://lists.gnu.org/archive/html/lilypond-devel/2006-02/msg00211.html

> My main concern is to make
> lilypond handle the above described situation automatically --
> lilypond's normal page breaking algorithm won't work because the left
> and right page for `primo' and `secondo' have be handled
> synchronously.  Here an example of the distribution of bars.  The even
> pages are on the left.
>
>    page         secondo            primo
>    ----         -------            -----
>      2           1-40               --
>      3            --               1-40
>      4           41-70              --
>      5            --               41-70
>
>                ...
>
> Of course I can manually insert \pageBreaks, but...  Just to be sure:
> Have you ever seen such primo/secondo scores?

And we have today the question from a French user.
Has anybody achieved this?  Or, at least, has anybody any hint about 
where to put the fingers?

Cheers,
Jean-Charles