Re: Chords in LilyPond

[Thomas Morley]

2017-05-29 7:04 GMT+02:00 Carl Sorensen <address@hidden>:
> On 5/28/17 5:53 PM, "Thomas Morley" <address@hidden> wrote:
>
>>
>>
>>Though, why adding a Œsemantics entry to the EventChord?
>>I'd suggest to write such an interpreter as a procedure which works on
>>the pitchlist ignatzek-chord-names currently has to work with
>>(including bass/inversion-info). Then write a printing-function which
>>works on the result of the interpreter.
>>Both public in guile, so that users can write different interpreters
>>and printing-functions as they like.

Hi Carl,

many thanks for your words about _what_ is tackled and what not. This
was not clear for me. I tried to reread the GSoC-projects-description
for this, but I couldn't find it...

There are still some details I'm not sure about. See below.

> There are three different problems in the Chords construct.
>
> 1) How to input chords.  We currently have two modes -- notemode and
> chordmode.  Notemode has no semantics.  Chordmode has semantics, but
> currently the semantics get largely tossed away (except for root, bass,
> inversion, IIRC).

As an example:

\new ChordNames \chordmode { c:1.3.5 }

I wouldn't agree we currently throw away semantics about this c-major-chord.
We identify bass/inversion (none here) and keep them.
Afaik, we don't _use_ anything else from this user input, even the
root is determined in ignatzek-chord-names.

> 2) How to determine a chord name.  For this, we currently have
> ignatzek-chord-names which interprets the pitches plus root, bass,
> inversion into a chord name.

See above for root.

> 3) How to display a chord name. This is currently mixed up with the
> determination of a chord name in ignatzek-chord-names.
>
> Charles's project is not to solve all three of these.  In fact, his
> project is not to completely solve any one of them.  Rather, his problem
> is to determine how best to save the semantics, so that assuming the
> semantics are properly entered in chordmode (probably including some
> extensions to the current chordmode, or maybe even a start from scratch
> rewrite, but that's out of scope for this project), the semantics will be
> kept as part of the chord, and thus be available for the
> chord_name_engraver to use when generating a chord name.
>
> When Charles is done, I hope that we will have a good internal
> representation for both the notes and the semantics.  The user will have
> the ability to define the semantics (at first, maybe only with Scheme, but
> eventually through good input).  And those semantics will lead to the
> desired output.
>
> Right now, we don't have control of the semantics; they're inferred from
> the pitches.  And that causes problems.
>
> Of course, we'll need to get good display routines (printing functions).
> And we'll need to get good input routines (for both chordmode and note
> mode).  And we'll need to get good infer-semantics-from-pitches routines
> (which Harm calls interpreters, I believe).  But if each of these can be
> separated from the others (which I hope Charles's project will do by
> capturing semantics properly in the EventChord structure), then I believe
> it will be easier to tackle all of the problems.
>
> Thanks,
>
> Carl
>

Do I understand correctly:
(1)
Problems with entering chords in note-mode is not really on the agenda
(in this case I'll not longer give such examples)
(2)
Finally something like the terminal-output of the fake below is aimed at:

chrd-test-III =
\chordmode {
    \displayMusic
    \withMusicProperty semantics
      #`((root . ,#{ c #})
         ;; or?
         (root . "C")
         (third . minor)
         (fifth . pure)
         (extensions . #f)
         (additions . #f)
         (bass . #f)
         (inversion . #f)
         (suspensions . #f)
         ;; else?
         )
    c
}

<<
  \new ChordNames \chrd-test-III
  \new Staff \chrd-test-III
>>

-->
(make-music
  'EventChord
  'semantics
  (list (cons (quote root) (ly:make-pitch -1 0))
        (cons (quote root) "C")
        (cons (quote third) (quote minor))
        (cons (quote fifth) (quote pure))
        (cons (quote extensions) #f)
        (cons (quote additions) #f)
        (cons (quote bass) #f)
        (cons (quote inversion) #f)
        (cons (quote suspensions) #f))
  'elements
  (list (make-music
          'NoteEvent
          'pitch
          (ly:make-pitch 0 0)
          'duration
          (ly:make-duration 2))
        (make-music
          'NoteEvent
          'pitch
          (ly:make-pitch 0 2)
          'duration
          (ly:make-duration 2))
        (make-music
          'NoteEvent
          'pitch
          (ly:make-pitch 0 4)
          'duration
          (ly:make-duration 2))))

And let the printing function work on the 'semantics?

So far, best regards,
  Harm