Re: Hara_kiri_engraver shouldn't handle both staves of a PianoStaff as separate single staves

[Kieren MacMillan]

Hi Valentin,

> this is, IMO, a bug: neither a Piano nor a Harp part
> should ever be reduced to a single staff!

I disagree, and there are many hand-engraved examples to back me up  
-- for example, Stravinsky's Petrushka (Edition Russe de Musique,  
1912) clearly shows the Harp I part as two staves with brace (most of  
the time) AND as a single staff (e.g., #29-#30), and the piano part  
as two staves with brace (most of the time) AND as a single staff  
(e.g., #27-#28).

Furthermore, as a composer (well, engraver), I *definitely* want the  
option to do either!

IMO, this should be a setting similar to connectArpeggios -- say,  
keepAliveTogether -- where the default is ##t, but it can be set to  
##f as desired. I suppose this could also be extended (as an  
interface) to ChoirStaff, StaffGroup, etc., for ultimate flexibility.

Best regards,
Kieren.