lilypond variable names

[Tim Nowaczyk]

  Using lily 1.3.41 I can't use variables with underscores in them in the \score
section.
\score
{
  \context ChoirStaff \notes
   <
    \treble_staff_context
    \bass_staff_context
   >
  \paper
   {
   }
}

gives the following...

star_spangled_banner.ly:285:11: error: unknown escaped string: `\treble': 
    \treble
           _staff_context
 
star_spangled_banner.ly:285:12: error: Have to be in Lyric mode for lyrics: 
    \treble_
            staff_context
 
star_spangled_banner.ly:286:10: error: parse error: 
    \bass_
          staff_context
 
star_spangled_banner.ly:286:16: error: Have to be in Lyric mode for lyrics: 
    \bass_staff_
                context
]]ly2dvi: Lilypond failed: lilypond  star_spangled_banner.ly 2>&1

When I remove the underscores from \treble_... and \bass_... it compiles fine.
Also underscores work in all other places I've tried them.

Thanks,
Tim Nowaczyk

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