Grace note introduces spurious symbol in Lilypond

Question

I have this simple code:

\new StaffGroup <<                                                                  
  \new Staff \with {                                                                
    instrumentName = "Vocal"                                                        
    shortInstrumentName = "Voc"                                                     
  } \new Voice = "voice" \relative {                                                
    a4 b c d                                                                        
  }                                                                                 
                                                                                    
  \new Lyrics \lyricsto "voice" {                                                   
    \lyricmode { A B C D }                                                          
  }                                                                                 
>>  

As expected it produces the following:

But the moment I add a grace note at the beginning:

\version "2.24.0"                                                                
\header {                                                                        
  title = "Jara si dil me de jagah"                                              
  composer = "Pritam"                                                            
}                                                                                
                                                                                 
\score {                                                                         
  <<                                                                             
    \time 4/4                                                                    
    \tempo 4 = 82                                                                
    \new StaffGroup <<                                                           
      \new Staff \with {                                                         
        instrumentName = "Vocal"                                                 
        shortInstrumentName = "Voc"                                              
      } \new Voice = "voice" \relative {                                         
        %\grace {s16}                                                             
        \grace {g16} a4 b c d                                                    
      }                                                                          
                                                                                 
      \new Lyrics \lyricsto "voice" {                                            
        \lyricmode { A B C D }                                                   
      }                                                                          
    >>                                                                           
  >>                                                                             
                                                                                 
  \layout {                                                                      
  }                                                                              
                                                                                 
  \midi {                                                                        
  }                                                                              
}    

this happens:

There is a spurious "C" symbol. How can I fix this?

Answer 1

Move the \time and \tempo commands inside the \new Voice block, like this:

...
\new Voice = "voice" \relative { 
    \time 4/4                                                                    
    \tempo 4 = 82                                                          
    \grace {g16} a4 b c d                                                    
}
...

This will prevent the extra staff from being created, and hence avoid the issue 34 bug from happening.