>> while it is probably not the best way to do it, here is a
>> pragmatical solution to the problem.
>
> Thanks a lot! Will try it soon.
Basically, it works great, but there are two problems (tested with
2.23.9).
* It doesn't print 'a 2' at the very beginning.
* Contrary to `\mark`, the 'a 2' should always be horizontally aligned
to a note column and not to prefatory matter like time or key
signatures.
The attached image shows the output of
```
{
\set Staff.staffAnnotation = "a 2" c'1 1 \break 1 1 1 \break 1 1
\key c\minor \time 2/2
\set Staff.staffAnnotation = "a 3" 1 \break 1
\set Staff.staffAnnotation = "a 4" \break 1 2
\set Staff.staffAnnotation = "a 42" 2 1
\unset Staff.staffAnnotation \break 1
}
```
Not sure whether this can be easily fixed without setting up a new
grob that doesn't interfere with `RehearsalMark` – sometimes it is
necessary to horizontally shift 'a 2' without influencing the
positioning of rehearsal marks at exactly the same spot.
Werner
