piano centered dynamics and dynamic text spanner override

[James E. Bailey]

Wow, I thought I was going crazy. If I use the template for piano  
centered dynamics, dynamic text overrides don't work unless they're  
attached to the proper voice context. Snippet follows.
\version "2.11.57"
\layout {
   \context {
      \type "Engraver_group"
      \name Dynamics
      \alias Voice
      \consists "Output_property_engraver"

      \override VerticalAxisGroup #'minimum-Y-extent = #'(-1 . 1)
      \override DynamicLineSpanner #'Y-offset = #0

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

      \consists "Skip_event_swallow_translator"

      \consists "Axis_group_engraver"
   }
   \context { \GrandStaff \accepts Dynamics }
}

global = { \key a \major }
musici = \relative c' { R1 \change Staff = "musicii" \voiceOne cis8 b  
a gis fis gis a b cis dis e fis gis4 e }
musicii = \relative a,{ \clef bass R1 \voiceTwo a8 b cis d e4 d e fis  
e8 d cis b }
dynamics = { \override DynamicTextSpanner #'dash-period = #-1.0  
\crescTextCresc s1 s1\< s2\!\> s2\! }

\score {
   <<
      \new GrandStaff <<
         \new Staff = musici << \global \musici >> \new Dynamics  
\dynamics \new Staff = musicii << \global \musicii >>
      >>
   >>
}
\score {
   <<
      \new GrandStaff <<
         \new Staff = musici << \context Voice = "musici" \global  
\musici >> \new Dynamics << \context Voice = "musici" \dynamics >>  
\new Staff = musicii << \global \musicii >>
      >>
   >>
}