Ableton sent me an email to tell me that the reason Live 9 is taking so long, is they've been working with Google to implement this:
https://www.youtube.com/watch?v=UiLSiqyDf4Y
Also, more insight to how me and a friend collab, as we are in the exact same situation (one is more technical, one throws some rockin good beats down).
We will get a cool idea that we want to work with, and move it to Dropbox, collect all and save.
We then proceed to fork our own versions of it "Cool Beat - Dude1.als" "Cool Beat - Dude 2.als"
This allows us to have 3 separate files at once, a master file, and our "in progress" versions.
We communicate to each other what we are working on so neither of us are working on the same channel strip.
Often times I'll say to him "Dude, think of some more bass line action -- I'm going to work on automation and flourishes on the drum and lead channels"
We'll each declare the channels we will be working on, as this is how we merge to the master. When we feel we've done our parts, we merge the parts we worked on. (Open the master set, then find the -Dude1 -Dude2 sets in the browser, and drag any relevant channels in). If we agree to the changes, we update our personal versions, and go back to work.
Obviously this isn't a great way to "Start" a song, or "End" a song, but it works okay for us once we have the general song structure laid out.
This method makes sure we aren't breaking each other's copies, and that we always have a structural master to use as a sort of "restore point." It also allows us to focus on whatever we are working on at the same time, without having to worry about what section my friend wants to listen to. If I need to demo a one bar loop for ten minutes to tweak some stuff, I can (god help me), and he can keep doing whatever he wants.
It is surprisingly easy to merge back to a master when we work in this manner. Of course, there comes a point where you need to just work off one computer at a time.
It isn't perfect for every situation, but I feel like this is the best I have available at this time. Until Ableton implements Live Multitask Mode.
