Re: Several thoughts for implementing accordion standard bass support

[David Kastrup]

Han-Wen Nienhuys <address@hidden> writes:

> 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.

Obviously, I have no clue whatsoever about what I am doing, and this is
the "poke with a stick until it works(TM)" approach.

Could you give a code example or outline for either of the possibilities
that you outlined?

-- 
David Kastrup