A basic question about ties

[Andrew Bernard]

Often I need to move the vertical position of a specific tie just a small amount. This is because I am using a custom flared tie function which draws flat ties with flared ends, and somtimes the ties sit right on a staff line, making them quite hard to read. This is the background, but not the main point of this question.

Setting the vertical position with an override, I thought naively that one could use \once before the override and only the following tie would be affected. But that does not work (2.19.48). I find I have to use \temporary and then issue a \revert call afterwards.

The following MWE illustrates. For the purposes of this very basic question I have used ordinary ties and not the special flared ties I mentioned above.

Pardon my very base ignorance, but does this relate to the fact the \once applies to the current musical moment, whereas a tie spans several moments? [I know this may be complete rubbish.]

Andrew

== snip

\version "2.19.48"

{

  \time 1/4

  \stemDown

  \temporary \override TieColumn.tie-configuration = #`((3.8 . ,UP))

  c''4 ^~

  c''8

  \revert TieColumn.tie-configuration

  s8 s

  \temporary \override TieColumn.tie-configuration = #`((2.6 . ,UP)

                                                        (-2 . ,DOWN)

                                                        (-7.2 . ,DOWN))

  <c' _~ g' ^~ c'' ^~>4 <c' g' c''>8

  \revert TieColumn.tie-configuration

}

== snip