RE: Transposable Fret Diagrams for Guitar

[Carl D. Sorensen]

Sebastien Gross wrote: 

>Indeed I find it usefull and more flexible than previous fret-diagram.
>Anyway both of them have advantages and disavantages :-(.
>
>fret-diagram:
>  * A:
>       - Can be placed almost anywhere
>       - can hold barre
>       - names are almost perfect when combining with a \chords
>         command.
> * D:
>       - Are not transposable
>       - are painful to defined and maintain a library
>       - work only in markup contexts
>       - does not handle color

>FretBoard:
>  * A:
>       - is a context
>       - is transposable
>       - is _human readable_
>  * D:
>       - cannot handle opened chords and barre chords when transposing
>       - cannot handle barre
>       - Names are not smartly handled
>       - does not handle color (shame on me I haven't tested :-/)
>

Color could probably be added to fret diagrams relatively easily,
regardless of whether they're made as markups or as items in a FretBoard
context.

> Great idea. Anyway I know almost 10 way do string an open C Major
chord.
> Then the standard chord reference _must_ be easilly configurable by
anyone.

I agree.  There are lots of ways to do an open C Major chord.  But if I
look at poplular guitar music books, over 95% of the fret diagrams shown
use the "x;3;2;o;1;o;" chord.  So for most people, I assume this would
be just fine.  In fact, that's what _I_ want to have happen.  I
recognize that others might want different performance, and that's why
the table would be configurable.

> Well one difficult point is to find a naming convention that might fit
to
> almost every chords. Hum not so easy. This would extent existing
chordnames
> I guess.

Lilypond already has a chord naming convention, used in \chordmode.  My
proposal is to use exactly that naming convention.

> I might be interrested to help sponsor this feature. But waiting until
> february may help in my personal accounts ;-).

February would work for me.

> Anyway can you give a dummy whished syntax that everyone agree?

To add a chord to the table, you'd do something like:

\set-fret-diagram \chordmode {d} #"2-(;5;2;4;3;-2;" 

(this is the fret-diagram-terse definition of a d chord barred at fret 2
with the C chord shape, if I did it right).

Then, to put stuff on a lead sheet you'd do

  mychords = \chordmode {c1 f}

<<
        \chords {mychords \transpose c d {mychords}}
        \FretBoards {mychords \transpose c d {mychords}}
        % entries for melody and lyrics would go here
>>

The result of this would be a context containing chord names: 

C   F  D  G

And under each of these chords would be a fret diagram.

The C diagram would be the standard from the library (as described
above)
The F diagram would be the standard from the library (probably 1st fret
barred with the E chord shape)
The D diagram would be the diagram defined in the \set-fret-diagram
statement above, instead of the library default (probably x;x;o;2;3;2;)
The G diagram would be the standard from the library (probably
3;2;o;o;o;2;)

If the user had some alternate fingerings to use for chords, that could
be accomplished by using \set\fret\diagram as described above, or by
just entering the actual notes to be played as part of the chord, and
letting FretBoards calculate the fingering as it currently does in 2.10
& 2.11.

Thanks,

Carl