Key list in lyricmode

[Simon Albrecht]

Hello everybody, (well, to be honest, hello David :-) )

I’m sorry, but I still need some enlightenment on the new alist variable 
feature. What’s the problem with the following snippet?

%%%%%%%%%%%
\version "2.19.39"

cantus.1 = { e' }
cantus.lyr.1 = \lyricmode { Mi }

<<
  { \cantus.1 }
  \addlyrics { \cantus.lyr.1 }
>>
%%%%%%%%%%%

I get

debug.ly:8:24: error: not a key
  \addlyrics { \cantus.
                       lyr.1 }

and so a non-music expression is getting ignored.
Basic testing didn’t quite show what the limitation is.

Best, Simon