<< \\ >> constructs and things that cross measures

[Ed Ravin]

In the LilyPond docs, it says:

   
http://lilypond.org/doc/v2.10/Documentation/user/lilypond/Basic-polyphony#Basic-polyphony

   These voices are all separate from the voice that contains the notes just
   outside the << \\ >> construct. This should be noted when making changes at
   the voice level. This also means that slurs and ties cannot go into or out
   of a << \\ >> construct.

And this is my problem - I've got a measure like this, where I'm trying to
draw a crescendo hairpin from the 3rd beat of this measure to the 2nd beat
of the next measure:

        << { d8. cs16 } \\ { f,8 g <f d'> \< <g b f'> <g c ef>2 \! }  \\ {
s4 s4 s4 s4 \< } >> |

Obviously this doesn't work - I get "warning: unterminated (de)crescendo"
on this measure and "warning: can't find start of (de)crescendo" on the \!
in the next measure.

What's the right way to deal with this kind of problem?  It happens
elsewhere where I'm trying to put pedal marks or slurs across measures.  Do
I need to make the << {} \\ {} >> sections "wider" to cover multiple
measures, and take out my bar checks for those measures?

In this particular case, the excerpt above is from the upper staff and I'm
actually trying to line the hairpin up with something on the lower staff.
I suppose I could put the hairpin on the lower staff, but then I'd get
the problem in the next measure, because the voice moves to the upper
staff there and the notes on the lower staff don't line up with where the
hairpin is supposed to end.