Adding a bass note

[Matthieu Amiguet]

Dear Lilyponders,

I'm a new user of lilypond and, for what I can say with the little experience 
I've got, I'm very happy with it.
The notes entry is much faster than what I'd have thought and the printout is 
beautiful (I had some trouble finding how to remove the "lily was here" tag, 
though...)
I've got a problem with added bass notes in a ChordNames context. For example, 
when processing this file with lilypond 1.8.1, 

------------- FILE ----------------

\version "1.8.1"

harmonies = \chords { 
  des1:maj7/+f  | g:m7.5-/+f
}

\score {
  \notes <
    \context ChordNames { \harmonies }
    \context Staff { \harmonies }
  >
  \paper{ }
}

--------- END OF FILE ---------------

the second chord does not get the "/F". Lilypond gets the notes right, as 
shown by the Staff context, but the bass F does not appear in the name of the 
chord.

I'm not sure I've got the right syntax for the chords, but all the other ones 
came out quite as I wanted them; this one doesn't want to....

Any Idea?

Thanks,

Matthieu

PS: Please cc the answer to me, as I don't seem to be able to subscribe to the 
list on the web site (I never get the confirmation mail).