What is void music?

[Dan Eble]

A. ly-syntax-constructors.scm has this.

   (define-public (void-music)
     (ly:set-origin! (make-music 'Music)))

B. music-functions.scm has this:
   ... (make-music 'Music 'void #t) ...

In lily-library.scm, the function collect-music-aux has the comment "void music 
is discarded”.  It seems to classify (B) as void music, but not (A).

I stumbled at this when I tried to define a predicate for void music, used (B) 
as an example, and found that it didn’t catch ##{#}.  I’m not sure what to do.

Are these different concepts that have been given the same name, or are they 
different valid representations of void music? ... or is the difference an 
error?

C. There’s also \void, which appears to be related in name only.

I don’t know if renaming is appropriate, but in case it is, I offer these 
suggestions:
  A) “null” music
  B) “annulled” music
  C) no change
— 
Dan