Until the 21st century it was still common to hear tandas of otros ritmos such as tropical (Argentine cumbia, or salsa), or swing, at many milongas. These might take the place of the milonga tanda and they helped to refresh the atmosphere. According to the testimony of Alberto Podestá and others, in the 1970s the milongas played 50% tango and 50% otros ritmos (other rhythms). The idea that an authentic milonga only plays tango music is relatively new.
In the 1990s it was still common to hear tandas of otros ritmos at many milongas. As late as 2006, when the city government passed a law (B.O.C.B.A. N° 2537) intended to support milongas, this stated: that the tanda of otros ritmos was a «fundamental part» of a milonga. Today (2015), most milongas do not play any otros ritmos. Many less experienced dancers, never having heard otros ritmos at the milonga, are under the impression that a traditional milonga only plays tango music.
So… you better learn that stuff even if you think Salsa is for wussy people