Re: MIDI: Automatic accent on notes starting bars

[Lukas-Fabian Moser]

> is there a way of automagically adding some volume increase ("accent") 
> in MIDI output to any note that happens to start on the first beat in 
> a bar?
>
> It seems a well-defined enough request to me so that it should be 
> perfectly possible to do this in scheme, but I'm afraid this exceeds 
> my very limited LilyPond-scheme abilites...
>
> Slight complication (maybe): In my scores, the metre changes all the 
> time, so one really would have to use the actual timing of a note.

Ok, so I tried to boldly dive into the hitherto unknown realm of 
engraver construction and came up with the following:

\version "2.19.82"

#(define (measure-position-from-context context)
   (ly:moment-main (ly:context-property context 'measurePosition)))

accent_downbeat_engraver =
#(lambda (ctx) (make-engraver
                (listeners
                 ((note-event engraver event)
                  (if (eq? 0 (measure-position-from-context ctx))
                      (ly:broadcast (ly:context-event-source ctx)
                        (ly:make-stream-event
                         (ly:make-event-class 'articulation-event)
                         (list
                          (cons 'midi-extra-velocity 20)
                          (cons 'articulation-type "accent")))))))))


\layout {
  \context {
    \Voice
    \consists \accent_downbeat_engraver
  }
}


\score {
  \relative {
    \time 2/4
    a8 b c b
    r8 a b4~
    \time 3/4
    b a8 b c d
    e4 e e
  }
  \layout {}
  \midi {}
}

This works fine in that it adds accents to any notes happening to start 
a new measure. But - and this would be crucial for my application - the 
accents do not survive in the MIDI output. (At first I thought that 
\consist'ing the engraver to the Voice context in the \midi might help, 
but alas...)

My guess is that I'm broadcasting an articulation event that suffices 
for the articulation being printed, but is either not "connected" to the 
actual note or is for some other reason missed by the MIDI performers.

How could I proceed?


Lukas