Can't make my (phrasing) slur end where I want it to with LilyPond

Question

I am trying to write a phrasing slur on a << {} \\ {} >> construction, and it seems like the slur doesn't end where it should.

My code is as follows :

%%%%%%%%%%
%% VERSION
%%%%%%%%%%

\version "2.20.0"


%%%%%%%%
%% SCORE
%%%%%%%%

\score {
    \relative c' {
        \clef "treble"
        \key c \major

        \time 6/8

        <f d'>4 \( \< <f d'>8 << { f'8. d16 <b f>8 } \\ { <g b>4 s8 } >> \! \) |
        <e c'>4.\( <g e'>\) |
    }
}

and produces :

The first slur begins at measure 1, and ends at the beginning at measure two, but I would want it to end on the last chord of the first measure (the f b). If I remove the second measure, there is no slur at all, even if I leave the command for it.

Any help is appreciated.

Answer 1

With the << { } \\ { } >> construction, you are essentially starting two new voices, one within the first pair of brackets and another voice within the second pair. But slurs cannot go across different voices. So, the only way to solve your problem is to put the notes where the slur starts into the same voice of the note on which the slur ends. The same is true for the hairpin: It needs to start in the same voice where it ends.

With the << { } \\ { } >> construction, the notes inside the first pair of brackets will be typeset as the first voice with stems and slurs upwards. Hence, you need to tell LilyPond to typeset the slur underneath the notes, for example using _\(.

So, you could write:

\score {
  \relative c' {
    \clef "treble"
    \key c \major

    \time 6/8
    << { <f d'>4_\(\< <f d'>8 f'8. d16 <b f>8\) <>\! } \\ { s4 s8 <g b>4 s8 } >> |
    <e c'>4.\( <g e'>\) |
  }
}

This should result in: