For example, the following ALMOST does the right thing already, by simply combining the two contexts and adjusting the MMR number Y-offset:
%%% SNIPPET BEGINS %#(ly:set-option 'debug-skylines #t) #(layout-set-staff-size 18.5) \layout { \context { \Staff \name customStaffDown \alias Staff \inherit-acceptability customStaffDown Staff \omit MultiMeasureRestNumber \override MultiMeasureRest.expand-limit = #1 } \context { \Staff \name customStaffUp \alias Staff \inherit-acceptability customStaffUp Staff \accidentalStyle piano \omit MultiMeasureRestNumber \override MultiMeasureRest.expand-limit = #1 } \context { \name PianoMMR \type "Engraver_group" \inherit-acceptability PianoMMR Dynamics \consists "Axis_group_engraver" \override VerticalAxisGroup.staff-affinity = #CENTER \override VerticalAxisGroup.nonstaff-relatedstaff-spacing = #'((basic-distance . 2) (minimum-distance . 1) (padding . 0.5) (stretchability . 1)) \consists "Dynamic_engraver" \consists "Multi_measure_rest_engraver" \hide MultiMeasureRest \override MultiMeasureRestNumber.direction = #DOWN \override MultiMeasureRestNumber.Y-offset = -1 } \context { \StaffGroup \name CustomStaffGroup \alias StaffGroup \inherit-acceptability CustomStaffGroup StaffGroup systemStartDelimiterHierarchy = #'(SystemStartBrace a b) } } % Begin Score Output theGroup = \new CustomStaffGroup << \new customStaffUp = "up" \relative c'' { \clef treble \key a \major \time 6/8 \repeat unfold 2 { r8 r8 <e e'> r8 r8 <e e'> | } R2.*2 | \repeat unfold 2 { r8 r8 <e e'> r8 r8 <e e'> | } \break \repeat unfold 2 { r8 r8 <e e'> r8 r8 <e e'> | } R2.*2 | \repeat unfold 2 { r8 r8 <e e'> r8 r8 <e e'> | } } \new PianoMMR { \repeat unfold 2 { s2.*2 | \compressMMRests { R2.*2 } | s8 s8 s8\ff s4. | s2. } } \new customStaffDown = "down" \relative c { \clef bass \key a \major \time 6/8 \repeat unfold 2 { r8 r8 <e e'> r8 r8 <e e'> | } R2.*2 | \repeat unfold 2 { r8 r8 <e e'> r8 r8 <e e'> | } \break \repeat unfold 2 { r8 r8 <e e'> r8 r8 <e e'> | } R2.*2 | \repeat unfold 2 { r8 r8 e r8 r8 e | } } >> \score { \theGroup \layout { \context { \CustomStaffGroup \override VerticalAxisGroup.staff-staff-spacing.padding = #4 } } } \markup \vspace #10 \score { \theGroup \layout { \context { \CustomStaffGroup \override VerticalAxisGroup.staff-staff-spacing.padding = #14 } } } \version "2.24.4" %%% SNIPPET ENDS Cheers, Kieren. __________________________________________________ My work day may look different than your work day. Please do not feel obligated to read or respond to this email outside of your normal working hours.