Hey, singers:
This Saturday at noon in the Boylston Plaza, Boston Pops peoples are organizing an event to try to set a World Record for the largest group of holiday carolers. Also, "for every person who participates in caroling, the Boston Pops will contribute $1 toward purchasing Holiday Pops tickets for children in underserved communities," which is pretty cute.
Further (but not a ton of) detail here:
http://www.bso.org/bso/mods/content1.jsp?id=40400017