'Can't Change Staff'

[Will Oram]

I know I'm posting to the list a lot with my questions; I'm trying  
out a lot of tricky notation snippets that, if successful, will  
produce free scores that truly show the kickass things lily can do.  
So...bear with me.

lily 2.7.8, OS X 10.4

I have centred dynamics working properly again (thanks, Trevor), and  
I intend to be making extensive use of staff changing. Auto-change  
won't be appropriate, so everything is done manually.

The following code should produce two treble lines: the bottom has g8  
followed by empty space, while the top starts on the bottom attached  
to the g8 notehead, then changes back up. Frankly, I don't get the  
logic myself, but it ain't my music.

(more after code)

---

\version "2.7.7"

\include "english.ly"

upper = \relative g'' {
    \clef "treble"
    \time 3/8

    \change Staff = "down"
    g16^(
        \change Staff = "up"
        g < eflat' g > g, \times 2/3 { < eflat' g > g, < eflat' g >) }
}

lower = \relative g'' {
    \clef "treble"
    \time 3/8

    g8_. s4
    g8_. s4
}

dynamics = {
    s8\pp s4

    s4.*4
}



\score {
        \context PianoStaff <<
        \context Staff = "up" \upper
        \context Dynamics = "dynamics" \dynamics
        \context Staff = "down" \lower
    >>

    \layout {
        \context {
            \type "Engraver_group"
            \name Dynamics
            \alias Voice
            \consists "Output_property_engraver"

            minimumVerticalExtent = #'(-1 . 1)

            \consists "Script_engraver"
            \consists "Dynamic_engraver"
            \consists "Text_engraver"

            \override TextScript #'font-size = #2
            \override TextScript #'font-shape = #'italic
            \override DynamicText #'extra-offset = #'(0 . 2.5)
            \override Hairpin #'extra-offset = #'(0 . 2.5)

            \consists "Skip_event_swallow_translator"
            \consists "Axis_group_engraver"
        }

        \context {
            \PianoStaff
            \accepts Dynamics
            \override VerticalAlignment #'forced-distance = #7
        }
    }
}

---

When typesetting, this message comes up...

Interpreting music...
warning: Change_iterator::process (): Staff = `up':
3piano.ly:7:8: warning: can't change `Staff' to `down': not changing  
to same context type:

        \change Staff = "down"

I imagine Dynamics is interfering, since everything else is Staff and  
there should be no trouble. Nevertheless, I know staff changes must  
be possible, because it is clearly visible in scores like this:  
http://www.mutopiaproject.org/cgibin/piece-info.cgi?id=535 . Yet,  
staring at the source, I can't find what I'm doing wrong for the life  
of me.

Any thoughts?

All the best --

I don't dare succeed
if change always comes first
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