Basic functions

[Jenifer Tribe]

I want to include a change of midi tempo at various points in a score, using something like

  \setSpeed #2 #120

where 

setSpeed =

  #(define-music-function

      (parser location scale speed)

      (number? number? )

    #{

       \set Score.tempoHideNote = ##t

       \tempo scale = speed

    #}

  )

I'm still using 2.18 I'm afraid, which still used the parser and location parameters..

I'm assuming this should be a music function rather than markup, but perhaps my arguments aren't numbers.

In this case the function is hardly worth it, but I want to base more complicated routines on it, and have failed at the first hurdle!

Jonathan