scaled durations and playback (was Re: cross staff bug?)

[Kieren MacMillan]

Hi Thomas,

> Scaling durations will avoid a second voice:

Just out of curiosity, how does that affect playback/MIDI?

Since the visuals are indistinguishable in the one- and two-voice versions, 
would it be "better practice" to keep it in two voices — despite the relative 
code clutter — in order to keep the playback "true"?
Thinking from a "how to document such things" perspective…

Thanks,
Kieren.