A few things aren't clear here ... mainly, what parts of your example are in a library file and what's in your actual song file? I'm assuming that you have created a file which defines one or more grooves and that is inlcuded into your song.
If you want to silence a voice/track it's easier to use the a "-" rather than a "z" ... honestly, I'm not sure if there is a difference without looking at the source. I always use -, but it shouldn't matter.
The manual might be misleading you a bit. When it says that grooves don't save or modify aria's it might not be totally clear what is going on. Assume this:
1. In a library file you define/create a number of grooves,
2. In the song file you read the library,
3. You call up a groove. Let's call it "G1",
4. Now you create a new (or override) Chord track. Let's call that C1.
5. Play a few bars. You'' be using whatever was set in G1 and have the track C1 playing.
6. Load (call) a new groove. G2.
7. Play a bar. You'll find that what you did to create C1 will be gone.
The difference is that with an Aria it doesn't disappear. Create an aria, load groove G1 and aria continues. In most cases this is what you want
In most cases I think people will be creating arias to play in addition to an existing groove. So this probably makes sense.
Now, what happens if you create arias in a lib file? Simple, the last aria stuff in the file will stay active. Remember, it is not saved into a Groove (defgroove ignores it). Nor is it recalled by a groove (can't recall what wasn't saved). Also, when using a lib file mma just reads it like any other part of your song file, but saves the current settings into a "special" groove which is recalled after reading the lib file. So, again, if you have:
Song file ... define an aria,
Song file ... load a groove
... during the reading of the lib file the aria will remain active
... in the lib file define some new stuff in the aria
... at the end of the lib, the newly modfied aria is active
return to the song file
... nothing from the lib file is active EXCEPT for the aria stuff
... the state of the song file is restored
I think the bottom line on this is that you probably should not define SOLO or ARIA tracks in lib files.
Getting back to your example, you really can't create a lib with a set of grooves it in with some having and some not having an active aria track.
I think you are trying to do create a number of different grooves, each a variation. So, just like chord, etc. tracks you create and modify the aria tracks thinking they are the same. They aren't. So, each defgroove/groove igores the aria stuff and whatever aria things you do are cumulatively stored.
Create aria tracks in the song file where you need them. Think of them like you would SOLO tracks.
Are we on the same page?