Re: Function to add a drone staff?

[Gilles]

Hi.

On Sat, 11 Apr 2015 22:07:43 -0700 (MST), Paul Morris wrote:
> Gilles Sadowski wrote
> > It happens when you use bar checks!
> > The sound is continuous without them but it would be quite annoying 
> > to
> > encode without their help for spotting mistakes... [I use version
> > 2.18.2.]
> >
> > In addition, the midi volume and instrument used for the drone must 
> > be
> > different from that of the main melody (in order not to overwhelm 
> > the
> > melody lines).
>
> Well, here's where the climb gets steep in trying to make this more 
> robust.
> See below where I added a "music-filter" step that filters out the 
> bar
> checks.  This solves the bar check problem, but there will surely be 
> similar
> things that will also need to be filtered out.

It works almost fine: no more stops between bars.

However I sometimes stumbled upon another problem: "dronified" full 
measure
rests ("R") generate a bar check warning.  It seems wrong because when 
I
changed "R" into "r" (and touched nothing else), the warning 
disappeared
(but so did the printed rests, of course).

I couldn't yet define a small example as the error comes and goes as I 
add
bars to the score! :-{

> These can be added just like for bar checks, but it's a tall order to 
> figure
> out which ones to filter out and which to leave in, given the large 
> number
> of "music types" to consider.  All the different types are found in 
> the
> LilyPond source code under scm/define-music-types.scm  (I glanced 
> through
> them, and even briefly tried it the other way around where you only 
> leave in
> note events, rest events, and... all other seemingly relevant events, 
> but
> this didn't work, as apparently more are relevant than I was leaving 
> in.)
>
> So that's what it will take to make this robust.  Alternatively you 
> could
> just add more types to filter out as new problems come up.
>
> You can uncomment \displayMusic (below) in order to see what's 
> causing
> trouble and needs filtering out.
>
> On setting the midi volume and instrument per voice... something like 
> what
> you originally had should do the trick.  Maybe something as shown 
> below with
> separate scores for midi and layout?

Yes, this solution is quite fine.

Thanks,
Gilles

> Cheers,
> -Paul
>
> %%%%%%%%%%%%%%%%%%%%%%%%
>
> \version "2.18.2"
>
> dronify =
> #(define-music-function (parser location drone melody)
>    (ly:pitch? ly:music?)
>    (let* ((melody-filtered
>            (music-filter
>             (lambda (m)
>               (not (or
>                     (music-is-of-type? m 'bar-check)
>                     ;; add other types to filter out here, as 
> needed...
>                     )))
>             melody))
>           (prev #{ #})
>           (current #{ #})
>           (art '())
>
>           (drone-part
>            (music-map
>             (lambda (m)
>               (set! prev current)
>
>               (if (and (music-is-of-type? m 'note-event)
>                        (ly:pitch? (ly:music-property m 'pitch)))
>                   ;; change the pitch
>                   (begin
>                    (ly:music-set-property! m 'pitch drone)
>                    (if (and (music-is-of-type? prev 'note-event)
>                             (ly:pitch? (ly:music-property prev 
> 'pitch)))
>                        ;; add tie to previous note
>                        ;; avoid overwriting existing articulations
>                        (begin
>                         (set! art (ly:music-property prev 
> 'articulations
> '()))
>                         (ly:music-set-property! prev 'articulations
>                           (append art (list (make-music (quote
> TieEvent)))))))))
>
>               (set! current m)
>               prev)
>             melody-filtered)))
>      #{ #drone-part #current #}))
>
> melody = \relative f' {
>   c4 d r e |
>   f r g a |
>   b c r e |
>   f r g a |
>   b
> }
>
> \score {
>   \new Voice {
>     \clef G
>     \melody
>   }
>   \layout {}
> }
>
> \score {
>   <<
>     \new Voice {
>       \set midiInstrument = "oboe"
>       \set midiMinimumVolume = #0.6
>       \set midiMaximumVolume = #0.7
>       \clef G
>       % \displayMusic
>       \melody
>     }
>     \new Voice {
>       \set midiInstrument = "accordion"
>       \set midiMinimumVolume = #0.2
>       \set midiMaximumVolume = #0.3
>       % \displayMusic
>       \dronify g \melody
>     }
>   >>
>   \midi {}
> }