Re: Chords in LilyPond

[Kieren MacMillan]

Hello Charles,

> I’m participating in the Google Summer of Code working on improving 
> LilyPond’s internal representation of chords.

As someone who uses chord names extensively, I’m thrilled that you’re tackling 
this!

> The goal here is to create a data structure that will represent a chord’s 
> semantics beyond just a list of notes in the chord.

Excellent goal!

> it would be much better to maintain the information provided by the user in 
> chord mode about the semantics of the chord through to the naming process.

Agreed.

> Here is a rough list of semantic information I believe should be included in 
> the data structure:
>       root note
>       quality (major, minor, augmented, diminished)
>       extension (7, 9, 11, 13, etc.)
>       added notes (6, 9, etc.)
>       suspensions (sus4, sus2, etc.)
>       alterations (flat-5, sharp-9, etc.)
>       omitted notes
>       added bass note
>       inversions

Yes.

> Some things that should be thought about:
>       Is the 7 an extension? Or included in the quality the chord? Or maybe 
> something else?

Since we’re starting from the ground up, can we not assume triadic harmony for 
the input (even if the output makes it look like we do)? For example, <c f bf> 
is not really, to my ears, a triadic chord with extensions and suspensions, but 
rather a quartic “triad”. Maybe there’s a way to handle this kind of thing (and 
others) elegantly?

> How do we deal with semantics that may overlap between these categories? For 
> example: is a sharp-5 an alteration or just an augmented chord?

A difficult question. Obviously, it would be great to allow the user — at the 
input, throughput, and output stages — to decide how to handle the information.

> polytonal/stacked chords (like Cmaj / Bbmaj)

Yes, please!

> I would love to hear any ideas from the user community about this. And beyond 
> the specific issues I’m talking about here, what aspects of LilyPond’s 
> support for chords do you believe should be improved or changed?

Here’s one off the top of my head: I would love to be able to easily 
input/output something like

  C    /B    /Bb

I’d add more now, but I’ve got to go to see some new opera.  =)

> I hope many of you are excited about this conversation.

I sure am! Please feel free to contact me on- or off-list with any questions.

Best,
Kieren.
________________________________

Kieren MacMillan, composer
‣ website: www.kierenmacmillan.info
‣ email: address@hidden