The example from the manual regarding merging of rests ( http://lilypond.org/doc/v2.19/Documentation/notation/multiple-voices#merging-rests) show a strange difference between whole measure rests and smaller rests. The crotchet rest in bar one is placed in the middle of the staff whereas the whole note rest in bar two is placed at the top (similar to the placement of the \voiceOne rest in the unmerged staff). Is this intentional or a bug? I would think that the correct placement would be in the middle of the staff.
(In the snippet below I've added a third staff showing the rest placement with a single voice in the staff. As expected lilypond places both rests vertically centered in this staff) \version "2.19.83" voiceA = \relative { d''4 r d2 | R1 | } voiceB = \relative { fis'4 r g2 | R1 | } \score { << \new Staff \with { instrumentName = "unmerged" } << \new Voice { \voiceOne \voiceA } \new Voice { \voiceTwo \voiceB } >> \new Staff \with { instrumentName = "merged" \consists "Merge_rests_engraver" \consists "Merge-mmrests-engraver" } << \new Voice { \voiceOne \voiceA } \new Voice { \voiceTwo \voiceB } >> \new Staff \with { instrumentName = "single" } \new Voice { \voiceA } >> } -- Jens Gyldenkærne Jensen Korshøj 226 3670 Veksø tlf: 2087 3360