Re: NR: Document \remove "Keep_alive_together_engraver" (issue 318580043 by address@hidden)

[Urs Liska]

Am 17.02.2017 um 09:21 schrieb David Kastrup:
> Urs Liska <address@hidden> writes:
>
>> Am 17.02.2017 um 08:34 schrieb address@hidden:
>>> Ok, I'll bite.  What kind of piano music is written like
>>>
>>> \score {
>>>   \new PianoStaff <<
>>>     \new Staff = "up" <<
>>>       \structure
>>>       \v.1
>>>       \v.2
>>>     >>
>>>     \dyn.1
>>>     \new Staff = "mid" <<
>>>       \structure
>>>       \v.3
>>>       \v.4
>>>     >>
>>>     \dyn.2
>>>     \new Staff = "lo" <<
>>>       \structure
>>>       \v.5
>>>     >>
>>>   >>
>>> }
>>>
>>> Because that is the example underlying your report.
>> Piano Music, at least starting with Liszt, all the way through into the
>> 20th century and until today.
>> The Ravel piece here requires five individual voices that are basically
>> distributed among three staves (frequent staff changes included), but
>> are printed partially on a three-stave PianoStaff and partially using
>> only the standard two staves.
>>
>> I feel it's natural to use PianoStaff here and to tell it to french
>> the middle system if empty.
> PianoStaff is explicitly for the case where you want staves to be
> frenched together.  Its name does not mean "Piano inside" but rather
> "Use frenching conventions common in piano music".

Then I'm tempted to file a bug report about PianoStaff being misnamed.
What else should the name PianoStaff imply than "Piano inside"? What you
are describing may be what developers have thought when inventing the
PianoStaff context, but for a user it is obvious that it refers to
"piano". Besides, "contexts explained" gives yet another explanation,
namely GrandStaff with support for grouped instrument names.

>
> And you actually would still not want it to french out multiple staves
> in an orchestral context: it should retain at least the two outer
> voices.

Then PianoStaff should have a (so-far-nonexistent)
Remove_all_but_two_staves engraver by default .

>
> So one solution might be to remove the middle stave from the
> Keep_alive_together_engraver's scope, with a proper setting of, uh,
> VerticalAxisGroup.remove-layer ?
>
> I'm a bit fuzzy on our current state in that area.
>
>> What I think I'll write to the docs now is that you have the choice
>> between resorting to GrandStaff (for the piano) or to remove the
>> engraver.
> There really is no point to removing an engraver when the sole purpose
> of PianoStaff is to add it.  

This is obviously a developer-centric way to see it. From any user's
perspective the primary purpose of PianoStaff is to enclose piano music
in it.

> Our documentation should focus more on
> keeping people on top of LilyPond rather than teaching them how to
> stumble along when they have no clue.  Because there are a whole lot of
> ways to do that and if we wanted to document all of them...

Well, so far no suitable way to create slightly extended (but common
since about 1830) piano notation has been documented. The obvious
solution (\RemoveEmptyStaves) doesn't work, and the suggestion to use
GrandStaff because PianoStaff is not actually meant for piano music is,
well, strange.

> I mean, we have the discussion lists for that.  Ask one question, get
> 10 answers.  But we don't have the room for 10 answers in the
> documentation, so we should pick the best one.
>

-- 
address@hidden
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