Originally the milonga was a slow and melancholic folk rhythm from the interior of Argentina. This is what we now call the milonga campera to distinguish it from the more modern subgenre of tango music.
During the early days of tango history, many tangos were little more then a milonga with habanera rhythm. These primitive tangos were common throughout the guardia vieja and then disappeared with Julio De Caro and the music of the guardia nueva. This is the original tango-milonga which Piana meant to bring back to life with Milonga Sentimental. By asking Homero Manzi to compose the lyrics, he also turns this old fashion tango into a sentimental song like those of Carlos Gardel.
Milonga that made your absence evocative milonga Milonga never to be sung at your balcony So you come back at night and go away with the sun To tell you sometimes that "yes" or to yell at you that "no" (casual translation)
“Milonga sentimental” was popularized by Mercedes Simone who performed it at the Teatro Solís in Montevideo with some success and recorded it for the first time in 1932. It quickly became a huge success and was recorded countless times by many others including Carlos Gardel, Charlo, Tania, Hugo del Carril, Fluvio Salamanca, Siriaco Ortiz, Adolfo Carabelli with Carlos Lafuente and Francisco Canaro with Ernesto Famá as well as with Ada Falcon.
Sebastián Piana recorded “Milonga sentimental” himself as a piano solo and with recitado by Julián Centeya. Other milongas by Sebastián Piana and Homero Manzi include “Milonga del 900” (1933), “Pena mulata” (1940) and “Milonga triste” (1936). Many of those new tango-milongas were recorded by orquestas típicas, including those of Francisco Canaro and Juan d’Arienzo.
Selles, Roberto. “El tango y sus dos primeras decadas (1880- 1900)” in La historia del tango: Primera epoca. Buenos Aires: Corregidor. 1977. Print.
Del Priore, Oscar, and Irene Amachástegui. Cien tangos fundamentales. Buenos Aires: Aguilar, 1998.