Rosendo Mendizábal was a pianist and composer of the early guardia vieja. He contributed to popularize tango at the end of the 19th century and to define it’s musical structure. He is the author of “El entrerriano“ (1897), which is regarded as the first tango in history.
Anselmo Rosendo Mendizábal was born in Buenos Aires in 1868 to a wealthy afro-argentine family. His father Horacio Mendizábal was an educated man and author of two published collections of poetry. Rosendo’s father died in 1871, leaving him with a house on calle Pilar (now Montevideo) and a fortune of 300.000 pesos. 
In his youth Rosendo Mendizábal studied the piano at a conservatory. Soon enough he dilapidated his inheritance and went on making a living with as a musician, teaching the piano in good houses and performing in cafes and nightclubs for the rest of his life.
Little is known about Rosendo’s life but at the end of the 19th century he was a regular in many establishments where tango was becoming popular. Lo de Hansen, Lo de la vieja Eustaquia, La parda Adelina, lo de Harguindegui and La casita de la calle Mexico are some of the places where he used to perform. He was particularly well known at Lo de Laura and at La casa de María la Vasca where his tango “El entrerriano” was presented to the public for the first time. 
Rosendo usually performed alone. He was occasionally seen with other musicians such as Luis Teisseire (flauta), Juan Carlos Bassan (Clarinette) and Vicente Ponzio (violin).  It was common at the end of the 19h century for tango to be performed by solo musicians or small bands with commonly available instruments such as guitars, flutes and violins.
“El entrerriano” was not the first tango strictly speaking. Many other tangos were composed and popularized before but “El entrerriano” was the first one to appear on partitions with registered author. Therefore it is the fort tango in historical terms. It is also the oldest tango still present in today’s repertoire.
Other tangos composed by Rosendo Mendizábal include “Don Padilla”, “Don Enrique”, “Tres Arroyos”, “El oriental”, “Matilde”, “El descanso”, “Le Petit Parisien”, “El final de una garufa”, “Ahí esta la cosa”, “A la luz de los faroles”, “Polilla” and “La entrerriana”. All his work was published under his artistic pseudonym “A. Rosendo”.
When recording technologies became available in Argentina around 1910, Rosendo Mendizábal was already suffering from paralysis. He died in 1913 at age 45 leaving no recordings.
 Tango: Cien anos de historia (Vol. II). Buenos Aires: Editorial Perfil, 1992. Print.
 Del Priore, Oscar, and Irene Amachástegui. Cien tangos fundamentales. Buenos Aires: Aguilar, 1998.
 Selles, Roberto. El tango y sus dos primeras décadas (1880-1900). La historia del tango. Corregidor, 1977. Print.