Re: How to set up polymetric situations

[Simon Albrecht]

On 21.07.2018 12:47, David Kastrup wrote:
> Simon Albrecht <address@hidden> writes:
> > On 21.07.2018 09:08, David Kastrup wrote:
> > > > It’s also sensible as well as intuitive and mnemonic to address the
> > > > Timing alias here:
> > > >
> > > > \set Timing.tempoHideNote = ##t
> > > Only if you move the Metronome_mark_engraver in polyrhythmic situations.
> > > If you don't and Timing is at Staff level...  The Midi is also affected
> > > at Score level.
> > This got me thinking – the only reason not to move
> > Metronome_mark_engraver is laziness or forgetting to do so.
> I don't think so.  Polyrhythm does not mean the loss of a common timing,
> and LilyPond does not implement it in that manner.  It means that the
> metric division of the passing time is different in different instrument
> groups.

Which may still entail different metronome markings for different groups 
or performers simultaneously, as in the example I gave, or for example 
in Britten’s War Requiem. True, it would require the user to really 
specify the metronome markings only in the top staff of the respective 
group (or remove the engraver from the other staves) – that’s a 
drawback, if not a huge one IMO.
Now if we created a new TimingGroup context which contains StaffGroup 
and Staff level contexts, doesn’t alter barlines &c. and \consists only 
of Metronome_mark_engraver – but I shouldn’t snowball on with major new 
inventions like that, I guess? It _would_ suit the semantics very well 
and be satisfyingly clear to document.

Best, Simon