Bonjour Sébastien et bienvenue sur la liste.
Une solution possible :
%%%
\version "2.18.2"
<<
\time 7/16
\new GrandStaff <<
\new Staff = "MD" \relative c' {
s16*7
<d ees f aes>16[
\change Staff = "MG" c, c
\change Staff = "MD" q
\change Staff = "MG" c
\change Staff = "MD" q
\change Staff = "MG" c
]
\change Staff = "MD" <d'! ees f aes>16[
\change Staff = "MG" c, c
\change Staff = "MD" \once \hide Accidental q
\change Staff = "MG" c
\change Staff = "MD" \once \hide Accidental q
\change Staff = "MG" c
]
}
\new Staff = "MG" { \clef C s16*7 s s}
>>
\new Staff = "Pedale" \with { \consists #Span_stem_engraver } {
\clef F \stemUp s16*7
s16
\once\override Stem.cross-staff = ##t
\once\override Stem.length = #15 %% <= à ajuster
<des e!>4*6/4
\once\stemDown
\once\override Stem.cross-staff = ##t
\once\override Stem.length = #-25 %% <= à ajuster
<des e!>4*6/4
\once\override Stem.cross-staff = ##t
\once\override Stem.length = #15 %% <= à ajuster
<des! e!>4*1/4
}
>>
%%%%%
Il doit y avoir plus élégant mais je ne l'ai pas sous la main...