What is it called when several people sing a song together in weired harmony!

It's a bit tough to put together, but you hear it in a french genre and it's almost entirely vocal!.
I'm sorry I can't put it together batter, but I know it's not choir but more like 20th century (I don't know if it's 40s, 50s, 60s or 70s) street and club musicWww@Enter-QA@Com

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