Our church had a flash mob at a local markets prior to Christmas. I liked the idea, but despite having been in a couple of church choirs and having singing lessons, my voice is akin to a groaning tree; thus, not for me.
The 'flash mob' had a trial run during morning church. It was great. One by one the choir, sitting randomly in the congregation, stood up and started singing. It was quite thrilling. Should do more such.
When I saw mention of this flash mob on Transverse City, and using a choir, I just had to post it.