Quote from the rottentomatoes synopsis:

For Duvall, the making of Assassination Tango is the culmination of a long-held dream, combining two worlds he loves so much. In the tango, Duvall finds an amalgam of contradictions, which is what makes it so appealing and also parallels his character in the film. “Tango is sweetness. Some people call it sensual. Some call it sexual. Others would disagree because a mother can tango with her son, a father with his daughter. It’s a very personal kind of thrust and a world that’s very special.”