not so nice slur

[Stefan Thomas]

Dear lilypond-users,
in the below quoted example (from the mutopia library) the slur
doesn't look very nice.
How can I change it? I now there is a snippet in the snippet repository
http://lsr.dsi.unimi.it/LSR/Snippet?id=134
but I don't understand it !
Thanks for Your help.
Here is the snippet:
%%%%%%%%%%% begin %%%%%%%%%%%%%%%%%%%%%
 \version "2.12.0"
 \include "english.ly"
  \relative g {
    \clef bass
    \key c \minor
    \time 4/4
                                % 1 - 4

   <g c ef g>4\(  <af c ef af> << { <ef' g>8. <d f>16 } \\
                                                             { <g, b>4
          } >> <ef g c ef>\) |}
%%%%%%%%%%%%%%%%% END %%%%%%%%%%%%%%%%