Re: how to reuse common header attributes

[Noeck]

>         { \transpose ds c \melody } % "ds" because "ef" yields a weird key

Thomas already posted the correct transposition, but just to emphasize:
If I understand what you want to do, the arguments of \transpose must be
inverted. You want to transpose from c to e flat:
 \transpose c ef \melody

The order in your snippet transposes from d sharp to c, i.e. a melody in
\key c \major is transposed to b double flat or a major.

Joram