Initial (but only initial) staff hiding

[Michael Welsh Duggan]

Here's the situation: I have a keyboard and vocal score that I am
typesetting.  I want the VocalStaff group not to begin until the system
with the first non-rest (interesting) event, but after that I want all
staff in the staffgroup to always exist, regardless of notes or lack
thereof.

I figured out how to tie the vocal staffs together using the
Keep_alive_together_engraver, but I can't use \RemoveAllEmptyStaves,
since that also will remove systems that contain only rests after the
first vocal note.  I tried a few things like setting
VerticalAxisGroup.remove_empty to ##f after the first note, but I
couldn't get that to work.  Can anyone suggest how I can do what I want
here?

-- 
Michael Welsh Duggan
(address@hidden)