creating chords like F/A(D/F#) with \chordmode { }

[Eby Mani]

How do i create chords like - B flat(G) or F/A(D/F#) with \chordmode { } ?.

I tried \markup "(G)", resulting the following : 
"error: markup outside of text script or \lyricmode"

Lilypond places everything in parenthesis to the next beat, "G" is moved to the 
next beat after B-flat, so is D/F#, parenthesis are not printed.

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\version "2.18.2"
global = { 
    \key bes \major 
        \time 4/4 
        \override Voice.Rest #'staff-position = #0
}

guitarOne = \chordmode {
bes2(g) f/a(d/fis)
}

melody = \relative c'{
\global
d'4. bes8 c4. a8      
}

\score {
        \new ChoirStaff <<
                \new ChordNames { \guitarOne }
                \new Staff <<
                \new Voice = "Mel" { \voiceOne \melody }
                \new Lyrics \lyricsto "Mel" { \VerseTwo }
                >>
>>
\layout { }
}

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