Analysis Bracket with dashed line

[Hugo Ribeiro]

Dear all, I am really stucked now...

I tried everything I know, but it didn't work. I managed to use the 
TextSpanner as brackets in the analysis example that I am typing. But 
there is a moment that one voice is related to two diferent brackets. I 
can do one, but I don't know how to put the other. The arrows were drawn 
using \markup inside the lyrics context, and the textspanner is aligned 
to the lyrics context. Below there is a minal example and attached is 
the jpg of the original.

Remember that this archive is part of a Lilypond-book project.

I am saying this because, I did lots of dashed-lines as markups, but 
when Latex compiles the lilypond file, everything changes places...

So, what I am looking for is something like a \startGroup with a 
dashed-line, so I can use in the upper part a \starGroup \endGroup and 
in the lower part of the same voice a \startTextSpan \stopTextSpan

Thanks a lot...

Hugo

p.s. Kent Kennan, Counterpoint Based on the Eigtheenth Century, Chapter 
10, example 13.

cap10ex13.ly
Description: application/extension-ly