Instantiating temporary staves with text

[Brent Annable]

Hello everybody,

I'm currently trying to produce a piece that is mostly on two staves, but at the end splits briefly into four staves and then back into two. I'm doing it by adding the extra staves to the top staff for those few bars and forcing line breaks so that it looks neat on the page. Everything goes fine until I try to add lyrics to the third line from the top (the line with the tenor clef) - using the \addlyrics command makes everything go haywire - the lyrics appear below the bass staff, staves cut off mid-page and the last section of the melody turns into chords instead of single notes. Commenting out the line of lyrics code fixes everything again, so as far as I can see it's purely the addition of the lyrics that causes the problem. 

I've reproduced the last few systems in a minimum (!) example to demonstrate, but because there's still a lot of formatting I've included the files as attachments. I hope that's OK. The only difference between the -right and -wrong .txt files is the commenting out of the \addlyrics command for the tenor staff.

I guess my question is: am I doing something wrong? Or is there a better way to do instantiate temporary staves than this?

Thanks for any help,

Brent.

test-right.txt
Description: Text document

test-right.pdf
Description: Adobe PDF document

test-wrong.pdf
Description: Adobe PDF document

test-wrong.txt
Description: Text document