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 by a friend (name on request) that the quasi-egalitarian Orthodox synagogues sprouting up in Katimon (1 and 2) or Washington Heights are all Carbachian, 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 a Hasidic shul, and more of it again among the Calbachians.
Is it the same in other Jewish denominations? And to what can it be attributed?