Re: Several thoughts for implementing accordion standard bass support

[Han-Wen Nienhuys]

On Tue, Jan 19, 2010 at 11:34 AM, David Kastrup <address@hidden> wrote:
> I am currently wrestling with accordion standard bass support.
> Basically, there are single bass buttons and chord buttons, and in the
> simplest mode, single basses are written in the -2 octave, and chord
> notes are wrapped/inversed to the -1 octave.
>
> When writing stuff, single basses are written with upper case letters,
> chords with lower case letters.
>
> Buttons may be combined.
>
> So a typical pattern may look like
>
>
> StdbassEngraver = #`((listeners
>                       (note-event .
>                        ,(lambda (engraver event)
>                          (let* ((pitch (ly:event-property event 'pitch)))
>                           (ly:event-set-property! event 'pitch

This looks wrong - engravers should not modify their inputs. Rather,
the engraver should create the Grob that you are interested in, or it
should acknowledge the grob created by another engraver.


> What about octave indicators?  Shouldn't c/c, be <c c' e' g'> rather
> than <c e' g'>?  Why doesn't even c:5.1/c have a 1 in the chord?

AFAIK, the /BASS syntax adds a pitch that has a special property set;
it is up to the engravers to decide how to interpret that.



-- 
Han-Wen Nienhuys - address@hidden - http://www.xs4all.nl/~hanwen