Re: strange error

[Mats Bengtsson]

> This file:
> 
> % Begin lilypond file.
> 
> melodya = \notes \relative c'' {
>         \stemUp
>         d4 c4 b4 a4
> }
> 
> 
> melodyb = \notes \relative c' {
>         \stemDown
>         d2 b2
> }
> 
> 
> \score {
>         \simultaneous {
>             \context Staff = melodya <
>                 \time 4/4;
>                 \clef treble;
>                 \melodya
>                 \melodyb
>             >
>         }
> 
>         \paper {
>             linewidth = 15.0\cm;
>         }
> }
> 
> % End lilypond file.
> 
> 
> generates errors as follows:
> 
> test.ly:13:12: warning: Adding note head to incompatible stem (type = 4):
>         d2 b
>             2
> 
> test.ly:14:1: warning: Adding note head to incompatible stem (type = 4):
> }
> 
> Lilypond seems to ignore the \stemUp directive.  This is using 1.3.120.  Is
> there any way to force an upward-pointing stem?

This is actually a feature of Lilypond. What happens is that both
\melodya and \melodyb are typeset as a single voice. Technically
this means that they are typeset by a single Voice context.
If you want to typeset them as two different voices with separate
properties (such as stem directions), you have to create these
contexts explicitly and give them separate names. The easiest
is probably to change the \score declaration to (untested):

\score {
            \context Staff = melodies <
                \time 4/4;
                \clef treble;
                \context Voice = melodya \melodya
                \context Voice = melodyb \melodyb
            >

        \paper {
            linewidth = 15.0\cm;
        }
}

I also removed the first \simultaneous declaration since you only
have a single staff. 

   /Mats