Split stem for different pitches on same staff level

[Han-Wen Nienhuys]

address@hidden writes:
> In the key of D-flat major, I wrote
> 
>       <d,16 bes'> <a' aes> <d, bes'>
> 
> and got for the middle chord two noteheads side by side, preceded by a
> natural sign with a flat sign superimposed.
> 
> Aside the obvious error (presumably a bug) of superimposing accidentals,
> this notation is incorrect.  Standard practice is to split the stem into a
> Y-shaped one that connects both noteheads, each immediately preceded by its
> accidental (if any).  

I think that standard practice is to not write such chords, use
cluster notation, or write <gis a> instead. I know about the Y shaped
stems, but they are hard to mend in with the current implementation
of stems and noteheads, and don't seem particularly readable.

>Is there any way to achieve this effect in LilyPond?

Yes: write a serious amount of C++ code to position the noteheads
correctly and draw the Y in between.

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