Triple slurring

[Urs Liska]

Hi,

I'm encountering triple slurs like in the attached examples. Discussion 
came to the conclusion that I should not "modernize" the notation using 
only one slur but regard it as an expressive means.

I'm somewhat at a loss at how to proceed best with that as LilyPond only 
provides "double" slurs (and I must admit that often they don't really 
look good). In order to create such slurred chords (I don't think there 
will be any cases of more than three notes, but in theory it should not 
be limited) I could fake the chord with polyphony, but that doesn't work 
nicely. "document.png" shows that the middle slur doesn't know about the 
lower voice and should be laid out quite differently, similar to a ties 
within a chord.

{
  \key c \minor
  <<
    {
      \voiceOne
      as'4 ( g'8 )
    }
    \new Voice {
      \stemUp
      \omit Flag
      d'4 _( es'8 )
    }
    \new Voice {
      \stemUp
      \omit Flag
      b4 _( c'8 )
    }
  >>
}

Is there any reasonable approach I could take here without creating fake 
polyphony and then formatting all slurs manually? It's not so much the 
work I'm fearing (so far I only see 5-8 instances of the problem) but 
rather the "uncleanliness" of the solution outlined above.

Any ideas?
(And particularly ideas that also work with LilyPond 2.18?)

Thank you
Urs

pathetique-1.png
Description: PNG image

pathetique-1.png
Description: PNG image

document.png
Description: PNG image