Re: Chords in LilyPond

[Robert Schmaus]

Hi Charles,

how good of you to send a summary of this thread. I was very interested 
in it as you wrote the first mail but couldn't reply right away. And 
when I could, the thread had already grown so huge, I just could not 
keep up all posts.
So it might well be that what I write has already been discussed. And it 
is quite possible that what I write is already covered by your plans 
without me realising it ... If so - sorry for the noise!


Anyway, there is one thing that I have trouble with in writing jazz lead 
sheets. It's about dominant 7th chords with #5. There are several 
versions of it (I'll use C as root): C7(#5), C7alt, C+7.

Seen solely as chord for comping, all of those could in principle be 
written as c : 7.5+ in chordmode, but the point is that they carry 
information about the underlying scale to be used in soloing (and of 
course melody). Basically, C7alt means that the underlying scale is the 
altered one, so

C Db Eb E Gb Ab Bb

whereas C+7 means that the underlying scale is the whole tone one

C D E F# G# A#

and I think that the notation C7(#5) might just be a variant of the 
altered chord. But I'm not sure right now - they both appear and might 
well have different implications about the underlying scale.


My point is, right now the only of distinguishing these chords is by 
using parts of the explicit scale in chord mode to distinguish them.
I've chosen to use

c : 7.5+     for C7(#5)
c : 7.5+.2   for C+7
c : 7.5+.2-  for C7aug

which of course doesn"t sound nice in the midi output. I can live with 
that - the midi is secondary for me, but it would of course be great to 
have some sort of interface to define "alt7 means to use 'alt7' in the 
ChordNames context of the layout but to use just (e.g.) < c e gis bes > 
in a Staff context or in midi".

I hope what I write makes some sort of sense ...


Another thing (which might have been discussed already on the thread) 
was: For reasons of clarity and brevity it sometimes is very helpful to 
write stuff like

Bb-7   /Ab    /Gb    /F

instead of having the root chord Bb-7 in each chord all the time. It 
would be great if there were an easy possiblity to suppress the chord 
and just leave the bass there. Right now that is not easily done ...


Anyway thanks for putting all that effort into this!
All the best,
Robert








Am 28.05.17 um 17:18 schrieb Charles Winston:
> Hi all,
>
> There have been some great discussions about new chord functionality you’d like 
> to see in LilyPond. The first step is defining the internal representation. 
> From there, I think all these issues can be much more easily solved. We have 
> the EventChord structure, which contains an ‘articulations and ‘elements entry. 
> The ‘elements entry contains some information about the root and inversion, but 
> otherwise it is a list of NoteEvents to be iterated over. My plan is to add a 
> ‘semantics entry whose elements will be semantic aspects of the chord:
>
>         -root
>         -quality of the third (minor, major, none)
>         -quality of the fifth (diminished, perfect, augmented, none)
>         -extensions (7, 9, 11, etc.)
>                         my plan for this is to have a list of extensions, each 
> extension associated with a bool indicating its presence in the chord,          
>          and associated with an alteration.
>         -added notes (6, 9, etc.)
>                         implemented similarly to extensions above
>         -suspensions (sus4, sus2, etc.)
>         -added bass note
>         -inversions
>
> Let me know what more should be added to this list.
>
> So after this is implemented, we have an internal representation of a chord, 
> EventChord, which contains both note information and semantic information, and 
> each of these can be utilized independently in different contexts.
>
> Let me know what you guys think.
>
> Thanks,
> Charles
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