Re: shortcut for creating new Staff "subclass" context?

[Kieren MacMillan]

Hi Dan, Neil, et al.:

> Does the following help?
> SoloVoice is a kind of Voice. UpperVoice and LowerVoice are kinds  
> of SoloVoice.

That's [relatively] self-evident. What isn't crystal clear — either  
in my mind, or (IMO) in the documentation — is why the following  
wouldn't work (or, perhaps better put, *what* wouldn't work if the  
following were used):

\context {
  \Staff
  \accepts "SoloVoice"
  \accepts "UpperVoice"
  \accepts "LowerVoice"
}
\context {
  \Voice
  \name SoloVoice
  %% \alias "Voice"
}
\context {
  \SoloVoice
  \name UpperVoice
  %% \alias "Voice"
}
\context {
  \SoloVoice
  \name LowerVoice
  %% \alias "Voice"
}

or alternatively

\context {
  \Staff
  \accepts "SoloVoice"
  \accepts "UpperVoice"
  \accepts "LowerVoice"
}
\context {
  %% \Voice
  \name SoloVoice
  \alias Voice
}
\context {
  %% \SoloVoice
  \name UpperVoice
  \alias "SoloVoice"
}
\context {
  %% \SoloVoice
  \name LowerVoice
  \alias "SoloVoice"
}

What *precisely* does \Voice [\SoloVoice, respectively] do, and what  
does \alias "Voice" [\alias "SoloVoice"] do? Do either of them "carry  
over" all of the \consists and \remove setting from its "parent"?  
What *isn't* carried over in either case?

This is what is unclear to me — despite studying the examples in  
engraver-init.ly and other snippets — and what I think needs to be  
clarified in the documentation. I've tried to figure it out by  
observation, but there appear to be other variables in play, so I  
haven't been able to grasp it concretely.

As soon as I think I have a handle on it, I'm happy to draft a doc  
patch for review — I just don't feel confident enough in my  
understanding [clearly!] to even attempt a first draft.

Thanks,
Kieren.