%% => http://lilypond.1069038.n5.nabble.com/How-to-make-an-object-take-up-no-space-td175271.html

\version "2.19.18"
\language "english"

testl = #'(
	(moveto 1 -4.5)
	(lineto 0 -2.5)
	(lineto 0 2.5)
	(lineto 1 4.5))

testr = #'(
	(moveto -1 -4.5)
	(lineto 0 -2.5)
	(lineto 0 2.5)
	(lineto -1 4.5))

\new Staff
{
	\clef bass
	\time 4/4
	\key c \major

	a,4 b, c d |
	\repeat volta 2
	{
		%\once \override TextScript.extra-offset = #'( -1.75 . -7.25 )
		a,4 
		-\tweak layer #-1 
		-\tweak extra-offset #'( -2.3 . -2.5)
		^\markup { 
		  \with-color #green 
		  \with-dimensions #'(0 . 0) #'(0 . 0)
		  \path #1 #testl 
		} b, c d |
	}
	\alternative
	{
		{
			e f g 
			\displayMusic {
			%\once \override TextScript.extra-offset = #'( 3.75 . -7.5 )
			a 
			-\tweak layer #-1 
			-\tweak extra-offset #'(4.4 . -3.1)
			^\markup { 
			  \with-color #green 
			  \with-dimensions #'(0 . 0) #'(0 . 0)
			  \path #1 #testr 
			} } |
		}
		{
			e f g a |
		}
	}
}