music function with access to context properties like currentBarNumber?

[Malte Meyn]

Hello list,

I would like to have somthing like

\version "2.19.22"
{
  \time 3/4
  % bar 1
  c'2.
  \skipUntil #5 % s2.*4
  % bar 5
  c'2.
  \restUntil #8 % R2.*2
  % bar 8
  c'2.
}

so I don’t have to count bars every time an instrument has a long rest 
(could also be helpful when composing, or, in a more advanced version, 
when skipping several bars with many time signature changes).

My first thought was “I need a music function that accesses 
currentBarNumber” but that (and, for the more advanced version, 
measureLength) is a context property. Now I don’t know how to get the 
context to this music function and making it return a (make-music 
'MultiMeasureRestMusic …). Attached is my first attempt but that returns 
only (make-music 'ApplyContext …).

Is this the correct approach? Or do I have to write an engraver? If so, 
where can I learn how to do that?

Thanks in advance,
Malte

restUntil01.ly
Description: Text Data