Groups for adult classical musicians

Hate to say this but I have not played classical for a while. One big reason is that it's more fun to play with others (for jazz at least I have iReal Pro to play with, or myself recorded) but I had a hard time finding like-minded people. We are quite familiar with the local orchestras for kids but not so for people like me. Then I came across this article on Strings: Get Out of the Practice Room, which is about many organizations (like ACMP) for adult amateur classical musicians. And it mentioned the Really Terrible String Orchestra in East Bay. I will definitely give it a try in the future.