key signatures and partcombine

[Eby Mani]

What should i do to show key signatures when using \partcombine ? you can see 
it doesn't render any key signature when \partcombine is used.

Thanks,

Eby.

*************
global = {
\time 4/4
\key f \major
}

descant = \relative c' {  d8 ([e]) f (g) a4 a d e8(d) d4 }

OrganRHOne = \relative c' { \clef treble
 a'4 f8 g a4 a f g a2 }

OrganRHTwo = \relative c' { \clef treble d8 [e] d e d4 e d e8 d d4 cis }

OrganLHOne = \relative c { \clef bass f8 <e g>8 <f a>4 f4 e a <d, g>4 e ~ <e 
a>4 }

OrganLHThree = \relative c { \clef bass d,2 d'4 cis d bes a4. g8 }

\score {
        <<
                \new Staff = "descant" << \set Staff.instrumentName = "Descant"
                \new Voice = "descant" { \global \descant }
                \new Lyrics \lyricsto "descant" { \verse } >>
                                
\new PianoStaff
        << 
                << \new Staff \with { printPartCombineTexts = ##f }{  
\partcombine \OrganRHOne \OrganRHTwo } >>

        \context Staff = lower << 
                \context Voice = OrganLHi  { \voiceOne \global \OrganLHOne  }
                \context Voice = OrganLHp { \voiceTwo \global \OrganLHThree }
 >>
        >>
>>
  \layout { }
}