Answering this question about nasal tones in popular music made me wonder. I've frequently heard songs from Mexico that pair two singers, one with a noticeably more nasal sound. For example:
Aerolina Carrilo - T3rcer Elemento
El Chuchumbe - Las Cafeteras (this group features two such pairs, one male and one female)
Un Poco Loco (from Coco)
I've heard this too often for me to think it's just a coincidence. Is there a name for these roles? Does anyone know the history of it?