invisible time signature example unclear (hymnody request)

[Ted Walther]

The example of doing an invisible time signature that is found in the
lilypond documentation really isn't very clear.

In many hymns, the time signature is 4/4, but it starts off with a bar
in 2/4, 3/8, or similar.

Oddly, in the second hymn I did, if I did the whole thing as 4/4,
lilypond complained that it couldn't find good places to break the
lines.  But when I made the first bar 3/8 and the last bar 5/8, lilypond
produced something almost identical to the original.  You can see what I
mean here:

    http://reactor-core.org/~djw/IsraelMarching.pdf

Can someone clarify how to do invisible time signature changes?

Failing that, can we have a "grace measure", similar to how we have
grace notes?

Ted

--
          It's not true unless it makes you laugh,                           
     but you don't understand it until it makes you weep.

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