partcombine on vocal parts

[JM Pim]

Hi there, I'm new to this list and pretty new to Lilypond in general so I 
apologise if I'm asking something stupid!

I'm currently trying to typeset a choral piece for SATB. At various points 
the four parts themselves split (e.g. the first basses sing {d1} while the 
second basses sing {g,2 a,}) but most of the time all of the basses, say, 
sing the same notes.

Using \partcombine ... I got the effect I wanted; mostly just single voice 
notes, stems and slurs in the right direction etc., chords when the rythmns 
of the two parts were the same and two separate voices when they weren't 
and so on.

However, I couldn't get the lyrics (which are the same for both bass parts 
and in this case have the same underlay) to display. Either nothing 
appeared or only where the voices split did lyrics appear.

Eventually I had to fudge and have another voice in parallel to the 
\partcombine that overrode the note heads to have zero width and hid all 
notes.

This is obviously not a very optimal solution.

Could I propose a new feature for this situation?

I would propose extending \partcombine to optionally accept two Lyrics 
contexts as well as Notes. Anytime both lyrics and notes are the same, you 
get output just the single line with one set of lyrics underneath, when 
either is different you get the split.

Note that it is common practice in choral scores to place two sets of 
lyrics next to a staff if the lyrics or underlay for each voice differs, 
e.g.

                         it      suddenly  changes
|----------------------------------X-X-X---------X-------------------
|--------------------------X------------------X----------------------
|--------X---------------------------------------X-----X-------------
|---X-------------------------x-----X--X-------------------X---X-----
|-------------X---X---X----X----------------X----------------------X-
 Start the same but then changes slightly from voice one to voice 2

I'm a computer science student (who learnt scheme in my first year!) so if 
someone could point me in the direction of the appropriate source file I 
could have a go at implementing it, though I have very limited knowledge of 
how Lilypond works I'm afraid :(

Thanks for reading this far!

Mark Pim