Re: Weird key sig accumulation

[David Kastrup]

Simon Albrecht <address@hidden> writes:

> Hello everybody,
>
> I’ve built some music functions to handle a large, multi-section
> piece, and ran into a strange problem, which I could boil down to the
> attached example.
> If the concat-part function is called on the \key expression multiple
> times in parallel, the \key expressions are accumulated in a way I’ve
> never seen before. Why would that be?

Because you are not copying the expression and still using it multiple
times.  A big no-no.  Consequently, \transpose works multiple times on
the identical expression.

If you use stuff multiple times, _copy_ it.  Because LilyPond will
generally _change_ expressions it is working on.

Multiple \transpose, multiple \relative, multiple other stuff: all that
you want to avoid occuring on the identical expression several times.

> \version "2.19.39"
>
> global.1 = { \key c \major }
>
> concat-part =
> #(define-music-function (al) (list?)
>    (make-sequential-music (map cdr al)))
> buildPart =
> #(define-music-function () ()
>    #{
>      \new Voice <<
>        \concat-part \global
>        { c'1 }
>      >>
>    #})
>
> \transpose c d <<
>   \buildPart
>   \buildPart
>>>

-- 
David Kastrup