Re: Controlling hairpin length

[David Sumbler]

On Tue, 2016-01-19 at 23:00 +0100, Thomas Morley wrote:
> %% a helper:
> #(define (look-up-for-parent name-symbol axis grob)
> "Return the parent of @var{grob}, specified by it's @var{name-symbol}
> in
> axis @var{axis} of @var{grob}.  If @var{grob} is already equal to the
> grob
> named @var{name-symbol} return @var{grob}.  If not found, look up for
> the next
> parent."
>  (let* ((parent (ly:grob-parent grob axis)))
>  (cond
>    ((not (ly:grob? parent))
>     (ly:error
>        (_"Perhaps typing error for \"~a\" or \"~a\" is not in the
> parent-tree.")
>        name-symbol name-symbol))
>    ((equal? name-symbol (grob::name grob)) grob)
>    ((not (equal? name-symbol (grob::name parent)))
>     (look-up-for-parent name-symbol axis parent))
>    (else parent))))
> 
> #(define (my-hairpin-minimum-length grob)
> "Sets @code{minimum-length} for @code{Hairpin}, if their left bound is
> not the
> @code{NoteColumn}.
> The visible length is actually the one, specified by an additional
> override for
> @code{minimum-length} or the default.
> If left bound is @code{NoteColumn}, default or specified
> @code{minimum-length}
> will take over."
>   (let* ((bound-left (ly:spanner-bound grob LEFT))
>          (sys (look-up-for-parent 'System Y grob))
>          (left-x-ext (ly:grob-extent bound-left sys X))
>          (not-note-column?
>            (lambda (g)
>              (not (and (ly:grob? g)
>                        (grob::has-interface g
> 'note-column-interface))))))
>      (if (not-note-column? bound-left)
>          (ly:grob-set-property! grob 'minimum-length
>            (+
>               (* (if (interval-sane? left-x-ext) (cdr left-x-ext) 1)
>                  (ly:grob-property-data grob 'bound-padding))
>               (ly:grob-property-data grob 'minimum-length)
>               (if (interval-sane? left-x-ext) (cdr left-x-ext) 0))))))
> 
> %% `myHairpinMinimumLength' tries to warrant the visible length of a
> Hairpin
> %% to be not less than the value of `minimum-length'
> myHairpinMinimumLength =
>   \override Hairpin.before-line-breaking = #my-hairpin-minimum-length
> 
> \layout {
>   \context {
>     \Voice
>     \myHairpinMinimumLength
>     %% default for 'minimum-length is #2
>     %% try different values
>     \override Hairpin.minimum-length = #2
>   }
> }
> 
I have now tested this latest version out on my string quartet score,
and it seems to have solved the problem of too-short hairpins.  I have
not checked through the whole piece thoroughly yet, but certainly in the
places where I previously had "decrescendo too small" warnings I now get
a hairpin of a sensible length.  (I have set Hairpin.minimum-length to
2.5).

Unfortunately I am still getting some over-long hairpins.  I think that
perhaps this has nothing to do with myHairpinMinimumLength, because I
was getting these long hairpins before you ever sent it to me - this is
one of the reasons I was going to set about tweaking hairpin lengths in
the piece.

The 2 bars I quoted before are:

% bar 14
        g8\< a b cs( ~ cs\mf\> b) d,\mp cs |
        g8\< g a g fs4\mf\> r\invP |
        d8\< e fs e as,(\mf\> b) r4\invP |
        e2\< d4\mf\> fs8(-\ten\mp fs)-\ten |
% bar 15
        b8 cs\< d e fs-\ten\> fs\! e d \time 3/2 |
        b,8\mp as\< b cs as-\ten\> b\! r4 \time 3/2 |
        r2 cs8-\ten\mf\> b\! r4 \time 3/2 |
        g8 e\< fs e fs-\ten\> d\! r4 \time 3/2 |

This is in \parallelMusic for a string quartet.

The decrescendo hairpins in bar 14 are now a reasonable length with the
new routine.  But the same items in bar 15 are far too long, in both
score and all parts: they are roughly the same length as the crescendo
hairpins earlier in the same bar, and thus the 5th and 6th quavers are
forced apart for no good reason.

I have tried substituting \! for my \invP markings, and replacing my
tweaked -\ten markings with standard -- marks.  I have also tried
removing the dynamics in the viola part - I wondered whether the mf,
which causes the viola hairpin to start a little later than the others,
was somehow upsetting things.

I have also searched all of the relevant input files for any mention of
Hairpin settings that I might have overlooked, but found none.

None of these experiments have changed anything: I still get a long
hairpin in bar 15, although bar 14 is fine.

As I said, it looks as if your routine is now working pretty well, and
the problem I am having with bar 15 (and a few others) is some peculiar
bug within Lilypond, but I can't figure out what is causing it to
manifest itself at this particular point.

Any suggestions you can make regarding this will, of course, be very
gratefully received!

David