Re: audible metronome in MIDI file?

[Jean Abou Samra]

Le 28/04/2022 à 04:31, Kieren MacMillan a écrit :
> I was thinking the very same thing — seems like a custom performer (or 
> engraver?) would be amazing for this. I hope Someone™ likes the idea 
> enough to code it up!



Well, I tried that yesterday: it has become possible to write Scheme
performers with change from David K. in the 2.23 series. I arrived at
the following, but ultimately decided not to post it because there
is a big bad bug: if there is  no note or rest or skip or some sort
of event at a point of time, a tick can't get added there. That makes
it practically unusable. A pity that Global_context::add_moment_to_process
is not Scheme-accessible ...


Regards,
Jean



\version "2.23.9"

#(define (Metronome_performer context)
   (make-performer
    ((process-music performer)
     ;; TODO: check is baseMoment is always accurate
     (let ((reg (ly:context-property context 'baseMoment)))
       (when reg
         (let* ((mp (ly:context-property context 'measurePosition))
                (strength
                 (cond
                  ((equal? mp ZERO-MOMENT)
                   'main)
                  ((integer? (ly:moment-main (ly:moment-div mp reg)))
                   'secondary)
                  (else
                   #f))))
           (when strength
             (let* ((source (ly:context-event-source context))
                    (cls (ly:make-event-class 'note-event))
                    (type (case strength
                            ((main) 'hiwoodblock)
                            ((secondary) 'lowoodblock)))
                    (props `((drum-type . ,type)
                             (length . ,reg)))
                    (ev (ly:make-stream-event cls props)))
               (ly:broadcast source ev)))))))))

\midi {
  \context {
    \name MetronomeTrack
    \type Performer_group
    %% This is veery ugly, but currently it is not possible to
    %% create audio items from Scheme performers, so ...
    \remove Drum_note_performer
    \consists #Metronome_performer
    \consists Drum_note_performer
    midiInstrument = "drums"
  }
  \inherit-acceptability MetronomeTrack DrumVoice
}

\layout {
  \context {
    \Score
    \accepts MetronomeTrack
  }
  \context {
    \Devnull
    \name MetronomeTrack
  }
}

%% Awful, but how to do better?? Of course, ideally the Metronome_performer
%% would be on Score level and create audio items itself, but for the time
%% being we have to use Drum_note_performer, which would duplicate drum 
notes
%% from all the score if it were put on Score level ...

#(set! toplevel-music-functions
       (cons (lambda (m)
               #{
                 <<
                   #m
                   \new MetronomeTrack { #(skip-of-length m) }
                 >>
               #})
             toplevel-music-functions))

\score {
  \midi { }
  \layout { }
  \relative c' {
    c'4( d8 e f g a b) c4( b8 a g f e d) c4-. c'-. c,2-^
  }
}