All collaborations remain open for alternative remixes

There is no such thing as a finished collaboration on wikiloops

All wikiloops collaborations start with an initial session template track and continue as others post remixes of the initial track, or remixes of any remix of the initial track - with a maximum depth of 5 re-remixes per branch.

An example:
Our sample collaboration starts with a drums-only track:
Session template: [just drums]
Then a user creates a remix, adding bass:
1st remix step: [drums + bass]
which again gets remixed by a guitar player:
2nd remix step: [drums + bass + guitar]
and so on, until the last track contains a total of six instruments.
Now, what we just assembled is one branch of remixes, but the fun does not stop here:
It is always possible to "branch off" at some point by posting an alternative remix,
for example, of the [drums + bass] version (or any other step except the 5th remix) from our example above.

Bottom line:
Just because a track already has a remix with a particular instrument does not mean you cannot do a separate version.

Read on with:
Navigating between remixes of one collaboration or
Creating and uploading a remix