Re: Issue 4622: create a <Part-combiner> class (issue 265260043 by address@hidden)

[nine . fierce . ballads]

I've marked the ticket as "needs work" for now.  I still have questions.
 It *would* be nice to be able to say

   \override Staff.partCombineParameter = #x
   \partcombine \one \two ...

and have the part combiner get its initial settings from the context.
The current implementation runs the combination algorithm as the
part-combine music is constructed.  But there is a way to defer
evaluating the elements of music until they are requested, isn't there?
Would it be safe to run the combination algorithm from a callback that
is not called until the part-combine music is able to look up its
initial parameters in context?  I'm not very clear on the sequencing of
things; I would worry that the elements might be needed earlier than
that, or that there might be a lot of recalculating, etc.

(I appreciate the time you're putting into this discussion.)

https://codereview.appspot.com/265260043/