"Cantor de Orquesta"

In the Golden Age of tango (1935-55), there were many famous dupla (duos) - orchestra / star singer. These singers were considered to be part of the orchestra, belonging to one particular orchestra at a time.
We feature one dupla (duo) in each program at Bailongo De Los Domingos.

Can you tell who they are in the photos below? (more contents coming in Jan.)