Rests in polyphonic and simple music in the same staff in LilyPond version 2.18.2.

[Mirosław Doroszewski]

Rests in polyphonic and simple music in the same staff in LilyPond
version 2.18.2.

1. In polyphonic music there are at least 2 voices in a staff.
2. It implies placing at least 2 rests in the staff.
3. It happens that composer wants to simplify notation of notes and
rests to be seen like one voice music.
4. It is set by command \oneVoice, and unset by commands \voiceOne,
\voiceTwo etc.
5. But when notation of rests are simplified in every voices, too:
i.e. c'4 \oneVoice r \voiceOne ... — an error occurs: "rest direction
not set".
6. Solution: simplifying visibility of rests only for first voice by
command \oneVoice, and writing s instead of r in every other voices,
i.e.:

voiceI = { \relative c' { \voiceOne e4 e f \oneVoice r \voiceOne } }
voiceII = { \relative c' { \voiceTwo c4 c d s } }
\score { \new Staff <<
  \new Voice = "1" { \voiceI }
  \new Voice = "2" { \voiceII }
  >>
}