aligning an arrow

[Robert Blackstone]

Dear all,

In the following example I would like to lower the arrow above the third bar to 
the level of those in bars 1 and 2, but up till now I have not found a way to 
accomplish it. Either the arrow stays at the same level or it disappears 
altogether.

%%%%%%%%%%%%%%%%%%%%%
\version "2.18.2"
\relative c' { 
\new Staff { \omit Staff.TimeSignature \clef "soprano"
<<  
{\stemUp a'4 \once \hideNotes  a \once \hideNotes a g }\bar "||" 
\new Voice {\voiceTwo \stemDown  f4 \set fontSize = #-4 \single \hide Stem e 
\single \hide Stem d^\markup { \combine \arrow-head #Y #DOWN ##f \draw-line #'( 
0 . 2) } \unset fontSize c |} 
>> 
<<  
{\time 5/4  \stemUp c' \once \hideNotes c \once \hideNotes c \once \hideNotes c 
d } \bar "||" 
\new Voice {\voiceTwo \stemDown c, \set fontSize = #-4 \single  \hide Stem d 
\single \hide Stem e \single \hide Stem f^\markup { \combine \arrow-head #Y 
#DOWN ##f \draw-line #'( 0 . 2) } \unset fontSize  g4 |} 
>> 
<< 
{\stemUp c \set fontSize = #-4 \single \hide Stem b %^\markup { \combine 
\arrow-head #Y #DOWN ##f \draw-line #'( 0 . 2) }
\single \hide Stem a \unset fontSize  g } \bar "||" \new Voice {\voiceTwo 
\stemDown { e4 \set fontSize = #-4 \once \hideNotes d^\markup { \combine 
\arrow-head #Y #DOWN ##f \draw-line #'( 0 . 2) } 
\once \hideNotes d \unset fontSize c } |} 
>> \bar "||" }
}%%%%%%%%%%%%%%%%%%%%%

Thanks in advance for any help.

Best regards, 

Robert Blackstone