invisible time signature

[Mark Dewey]

Hello,

I was wondering how to make an invisible time signature.  I'm notating a long
piece of music, and thus it seems ideal to use multiple scores (since the number
of clefs changes throughout the song), and I want it to 'look' as if it were a
single score (i.e. the time signature only needs to be displayed at the
beginning of the first score).

Also, I'm kind of wondering if there's a better way of adding an extra clef
half-way through the song (without facilitating the need for lots of skips).

Thanks!