Celeste Winant has written about the tendency of multiple choruses in the Bay area to perform on the same weekend, which happens at least three or four times a year. She is also trying to do something about it.
There are plenty of reasons for choruses to do some schedule coordination. We're all in competition for the same pool of free-lance musicians. We all want to sing in the same venues. Some choristers sing in multiple choruses. Choristers are also audience members, and we want to hear what other groups are doing.
I think we might need something like the Gotham Early Music Scene to help out. This group plans to "help [early music groups in NYC] with marketing, ticket sales, merchandising and assembling the financial data required for grant applications."
Sheer genius: take this specialized work off the hands of small performing groups that don't have the time or infrastructure to do the best possible job with those tasks. Can we figure something out in the Bay Area to do this for choruses?