Collabrative Music Software

Hey y'all!

My friend and I are writing a musical, and I'm curious to find out if anyone knows of a website or software that we can both edit the sheet music, and it would be prefered if it were free. I currently use MuseScore, and he is using the free version of Noteflight. 

I've done a lot of market research in this area, and as of now, Noteflight is your best bet for online music notation. However, you may be interested in what I am doing over at Music Jotter. What I am building is Finale level quality, but cloud based. Thus, it won't be free, but if you or your friend want to become early adopters to help me fix problems, I will be opening a Patreon soon. I also encourage you both to follow my Youtube channel if you are into music notation. The more support I receive, the faster I can get Music Jotter pushed out into the world.

I know its not the answer you were hoping to hear, but there's not much out there with regards to music notation right now. It's a very difficult type of software to create.