STEM COLLISION

[MX]

Bonjour à tous, Hi all.

On the attached picture [original.png] at the sopano voice, at the 
beginning of the measure, there are at the same time an F quarter note 
with a mordent (only for this note) and a dotted eighth note A. In the 
original score, these notes are well distinct and the mordent is applied 
only on the A quarter note.

How to do that with Lily ? I tried with the attached test file and look 
at the corresponding result.png. I tried to shift the A with an 
\override NoteColumn #'force-hshift  without  any good result.

Thank you in advance. Merci.

M.X.

% -*- mode: LilyPond ; coding: utf-8 -*-
\version "2.6.4.3"
%\include "italiano.ly" 



\header{
    title = \markup {\center-align { "Offertoire" "extrait du" "Premier livre 
d'Orgue"} }
    subtitle = ""
    piece = "" 
    instrument = ""
    composer = "Jean-François Dandrieu (1681-1738)"
    copyright = "Creative Commons Attribution-ShareAlike 2.5"
    mutopiainstrument = "Organ"
    style="Baroque"
    footer = "Mutopia-2006/??"
   
}

#(set-default-paper-size "a4")

global = {
  \key a \minor
  \time 4/4
}

soprano = \relative c'' {
  %<< {fa4^\mordent } \\ {la8.  sol16}>>  sol8.^\prallprall fa16 fa4. la,8
  << {f4^\mordent } \\ {\stemUp a8.  g16}>>  g8.^\prallprall f16 f4. a,8
}

alto = \relative c' {
  %do8 re8 mi4 <la, do>4. re,8
  c8 d8 e4 <a, c>4. d,8
} 

tenor = \relative c' {
  s1 
} 

basso = \relative c {
  %fa8 sib8 do8 do,8 fa8 sol8 la8 fad8 
  f8 bes8 c8 c,8 f8 g8 a8 fis8 
}

\score {
  
  \context PianoStaff <<
    \context Staff = "dessus" <<
      \global
      \clef violin
      \context Voice = "soprano" {
        \voiceOne \soprano
      }
      \context Voice = "alto" {
        \voiceTwo \alto
      }
    >>
    \context Staff = "basse" <<
      \global
      \clef bass
      \context Voice = "tenor" {
        \voiceOne \tenor
      } 
      \context Voice = "basse" {
        \voiceTwo \basso
      }
    >>
  >>
  \layout {}
  
  \midi { }
}