Making a quarter note look like a half note?

[Kilian A. Foth]

Hello world,

I need to create a tie that stops in the middle of a bar (the final
note of a piece should carry a tie to nowhere to indicate `laissez
vibrer'). Tying to an invisible grace note does not work -- it would
create an additional bar. I reckon I can fill the 2/4 bar with a
quarter note and tie it to an invisible second quarter:

\score {
  \new PianoStaff <<
    \new Staff { 
      \time 2/4 \relative c'' {
        <c e g c>2~|<c e g c>2~|
        <c e g c>4~ \hideNotes <c e g c> \unHideNotes \bar "|."
      }
    }
    \new Staff { \clef bass \time 2/4
      \relative c {
        <c e g>2~|<c e g>2~|
        <c e g>4~ \hideNotes <c e g> \unHideNotes \bar "|."
      }
    }
  >> 
}

But how can I make the quarter notes look like half notes? I know I
can change the note head *style* with something like

 \once \override NoteHead #'style = #'cross

But I don't need a different style, but another symbol from the *same*
style. What property do I need to override? Or do I have to go all the
way and reprogram the chord with \applyoutput?

(BTW, searching the list archives appears to be broken. I get
no results for any search whatsoever.)


-- 
Kilian Foth                                    Phone +49 40 42883-2518
AB NATS, FB Informatik                         Fax   +49 40 42883-2515
Universität Hamburg
Vogt-Kölln-Str. 30
22527 Hamburg