Determine event at the same time in other voice

[Urs Liska]

Hi all,

how could I determine if at any given point in time there is another 
event in another voice or not. Concretely: If I have a certain rest, can 
I know if another rest of the same length is in another voice?

I would like to explore the idea of having a command like

\mergeSimultaneousRests

which would take care of setting \voiceOne in one voice and \once\omit 
in the other voice(s) to make that typical kind of notation more 
straightforward to use. I find it slightly embarassing that we have to 
do that manually for each instance.

Best
Urs