Explicit durations in Lyrics behaving strangely

[Peter Chubb]

Hi,
        I'm trying to use the Adeste Fideles tune from
Mutopia http://www.mutopiaproject.org/cgibin/piece-info.cgi?id=367 
I ran convert-ly on it.  It uses explicit durations on the lyrics.  I see
many warnings: 

adeste.ly:94:18: warning: Lyric syllable does not have note. Use \lyricsto or 
associatedVoice.
    A4 -- des2 -- 
                  te,4 fi -- del2 -- es,

The output looks OK.  Why does Lily care about associated voice, if
all lyrics have explicit durations?

--
Dr Peter Chubb  http://www.gelato.unsw.edu.au  peterc AT gelato.unsw.edu.au
http://www.ertos.nicta.com.au           ERTOS within National ICT Australia
A university is a non-profit organisation only in the sense that it
spends everything it gets  ... Luca Turin.