The first picture that comes to mind are black protesters singing "We Shall Overcome" during the civil rights struggle. Then, I remember the communists, way back when the Party was still the sort of thing a well-meaning bright-eyed humanist might join, also had songs. And so did the ficitional residents of Orwell's famous farm.
Now I am being told that the quasi-egalitarian Orthodox synagogues are all Carlbachian, ie: they sing as much as possible. This seems to be the Orthodox Jewish trend: the further to the left you go, the more likely you are to encounter a singing minyan. There's more of it in an MO shul than in a Hasidic shul, and more of it again when you reach the Calbachians.
Is it the same in other relgions? Are Muslims who want social change more likely to sing? And to what can it be attributed?
Search for more information about the big sing along we banned from Facebook Jewish bloggers have planned at4torah.com