You might find this interesting, just came across it today!

Unofficial Google Music API in Python, quite well documented. http://unofficial-google-music-api.readthedocs.org/en/latest...

About to get started writing a little script that will take care of synchronising my library with my google music one, and automatically uploading those that it can't find a match for. A few of my friends also use it, so I was also thinking of making a little tool that would allow us to compare our libraries and show us what each other are missing etc.