Re: Tweaking in an engraver

[David Kastrup]

Vaughan McAlley <address@hidden> writes:

> On 20 July 2015 at 05:01, David Kastrup <address@hidden> wrote:
>> An engraver has the advantage that it is at the latest possible point in
>> the pipeline.  But it might be too late to actually change pitches
>> before other engravers get to see them.
>
> From what Scheme-fiddling I’ve been doing, it seems that the results
> of display-scheme-music are yet to be “folded” (my word). So something
> like:
>
>
> %%%%%%%%%%%%%%%%%%
> \version "2.18.2"
>
> myMusic = \new Voice {
>   <<
>     { c'1 s }
>     { s1 d' }   % equivalent (typographically) to { c'1 d' }
>   >>
> }
>
> \displayMusic \myMusic
>
> %%%%%%%%%%%%%%%%%%%
>
> …will give (as it probably should) an expression with
> 'SimultaneousMusic. Is it possible to created a “folded” version in
> Scheme, or is that done by the engravers later, when it would be too
> late to fiddle with?

No "folded version" is usually created at any time.  The
Simultaneous_music_iterator is running at interpretation time and is
walking through all parts of the music in parallel, generating stream
events in musical time order.  Those are usually not collected even
though the Part_combine_iterator or Auto_change_iterator or \addQuote do
record the results for later use.  But those are exceptions.

-- 
David Kastrup