Scheme void function problems

[Simon Albrecht]

Hello,

I’m experimenting with an implementation of automatic tagline language 
selection and currently have two problems with the void function 
\language that I adapted from music-functions-init.ly:
– I can’t get the first, optional argument to work; it needs to be 
explicitly given or Lily will take the string as first argument – 
although it’s required to be a symbol.
– The define in the second clause to cond doesn’t work: there are two 
errors due to output-language being an unbound variable.

Help! :-)
Simon

PS:
A short note on the intended design of the function: I want to achieve that
\language input "deutsch"
only sets the note names language,
\language output "deutsch"
only selects the german tagline and
\language "deutsch" or
\language general "deutsch"
does both. (See discussion on ly-bug)

tagline-b.ly
Description: Text Data