Re: tempo percentage

[Gianmaria Lari]

On 8 November 2017 at 18:15, David Kastrup <address@hidden> wrote:

Gianmaria Lari <address@hidden> writes:

> Talking about midi, is there any way to to reduce or increase the tempo of
> some measures by a certain percentage instead of setting it to an absolute
> value?
>
> For example instead of:
>
> \tempo 4=100 a b c d
> \tempo 4=110 e f g a
>
>
> something like
>
> \tempo 4=100 a b c d
> \tempo 4=currentTempo*1.1 e f g a
>

Well, it's not pretty (but then one can try wrapping the prettiness into
a music function), but here goes:

I tried to make it pretties. Here it is the code:

\version "2.19.80"

increaseTempo = 

#(define-music-function (factor)(number?) #{

  \context Timing \applyContext

  #(lambda (c)

       (set! (ly:context-property c 'tempoWholesPerMinute)

             (ly:moment-mul (ly:context-property c 'tempoWholesPerMinute)

               (ly:make-moment factor))))

   #} )

\score {

  {

    \tempo 4=100

    a b c' d'

    \increaseTempo 3

    e' f' g' a'

  }

  \midi {}

  \layout {}

}

This works ok only when \increaseTempo argument is integer. If i try \increaseTempo 2.5 it doesn't work. How to fix it?

Thank you, g.