tie collision

[Werner LEMBERG]

The following example produces heavy tie collisions:

  <c1 d f g> ~ <c d f g>

I think the following algorithm handles ties between chords
gracefully:

  For an up-tie, first check the left chord.  If the start note is the
  lower note of a second interval, shorten the tie.  Then check the
  right chord.  If the end note is the upper note of a second
  interval, shorten the tie if the next higher hote is the lower note
  of a second interval, and the distance to it is smaller than a
  fifth.

Here the mirror rule for down-ties:

  First check the left chord.  If the start note is the lower note of
  a second interval, shorten the tie if the next lower note is the
  higher note of a second interval, and the distance to it is smaller
  than a fifth.  Then check the right chord.  If the end note is the
  upper note of a second interval, shorten the tie.

Still missing is the case of broken ties where the ties in the new
staff have to cross the accidentals...