\version "1.3.146"
\header {

texidoc = "If you specify two different key sigs at one point, a
  warning is printed."

}

\score { \notes
\context Voice <
 { \key cis \major cis4 \key bes \major bes4 }
 { \key cis \major fis4 \key es \major g4 }  
>
}
