She was one of the singers who emerged in the 1920s along with Azucena Maizani, Libertad Lamarque, Ada Falcón, and Rosita Quiroga, who created the female voices of tango.

Her period of greatest popularity came in the following decade, when she led films like Los isleros (1951), considered her best performance, Guacho (1954) and Mercado de abasto (1955).

Her role in 1974 as La Madre María, directed by Lucas Demare, was highly acclaimed as was her collaboration with Alejandro Doria in Los miedos (1980).

[7] At age 9, she was diagnosed with tuberculosis and sent to a farm near Magdalena, where she worked in exchange for room and board,[9] milking cows, cutting yerba mate and grilling food for the workers.

[6] At age 12, she returned to the tenement to live with her mother[9] She went to work in a seedy club called Ba Ta Clán, where the chorus girls became known as bataclanas.

[9] Around 1917, Merello began working as a showgirl in the Rosita Rodriguez Company at Teatro Avenida and debuted in a play called Las vírgenes de teres.

[15][16] Some claim there were three films, Buenos Aires tenebroso (1918), a crime drama; La garra porteña; (1918), and Amor de primavera (1918–1919) both directed by Juan Glizé and Vicente Marracino.

[3] In 1923, she got a part as a show girl in the revue Las modernas Scherezadas playing at the renowned Teatro Maipo, performing with the stars Luis Arata, Pepe Arias, and Marcos Caplán.

[22] In 1925, she performed in the revue Mujeres, flores y alegría,[23] in which she sang the tango "Pedime lo que Querés" by Francisco Canaro with lyrics by Juan Andrés Caruso.

[3] Between 1929 and 1930, she recorded twenty songs for the label RCA Victor, including "Tata... Llevame pal centro", "Che... Pepinito", and "Te has comprado un automovil".

Libertad Lamarque had been playing the role of Doce Pesos in "El conventillo de la Paloma" for two years and had over 1,000 performances.

[32] In 1935, she starred in Noches de Buenos Aires directed by Manuel Romero with Fernando Ochóa, Severo Fernández and Irma Córdoba.

[35] That same year she followed in a dramatic role in the film, La fuga[6] under the direction of Luis Saslavsky which featured the tango "Niebla del Riachuelo" performed by Merello and written by Enrique Cadícamo.

[27][38] Merello was in the play Sexteto by Ladislao Fodor, under the direction of Edmundo Guibourg opened in 1941[19] in Montevideo at the Teatro Artigas, starring Gloria Guzmán.

[42] In 1945, she performed in Una mujer y un hombre by Pelay under the direction of Manuel Romero[19] and then Merello brought Sexteto from Uruguay to Argentina and premiered the play in Mexico.

It was so successful, the play was turned into a movie of the same name directed by Luis Mottura in 1950[44] starring Merello with Guillermo Battaglia, Gloria Ferrandiz and Alberto de Mendoza.

[52] Merello also started appearing at this time on a weekly radio show called Ahora habla una mujer which aired Monday to Friday at 20:30[53] on the Private Broadcasting Network.

In 1950, Merello starred in one of her most acclaimed films, Arrabalera, directed by Tulio Demicheli in his solo debut[54] with Santiago Gómez Cou.

[59] 1955 proved to be a busy year as she made three other films: Para vestir santos, El Amor Nunca Muere and La Morocha.

[61] Her last film in the period would be La morocha directed by Ralph Pappier with Alfredo Alcón and Luis Arata, which was not released until 1958,[62] because of the 1955 military coup d'état which ended the presidency of Juan Perón and sent many into exile.

[64][65] Though Merello was not political, her success under the Perón regime made her a target and she was accused of trafficking Ceylon tea by an investigating commission.

[67][68] At one point, she worked for a time in the circus[38] and in 1957, she returned to Mexico and did a television production of Eugene O'Neill's Before Breakfast (Antes del desayuno).

[69] She immediately returned to the stage in 1958 with two productions: Amorina by Eduardo Borrás followed by Luces de Buenos Aires[19] starring Merello, Hugo del Carril and Mariano Mores.

[71] She returned to the theater in 1962 with La Moreira by Juan Carlos Ghiano and the following year performed Carolina Paternóster by Eduardo Pappo.

Merello hosted a talk show, Charlando de todo con Tita on channel 13 from 1970[80] to 1971 where she told anecdotes, sang and gave advice.

She starred in the production of En vivo y al desnudo by Gerardo and Hugo Sofovich in 1973[19] and, in 1974, made the film La Madre María under the direction of Lucas Demare,[82] which was well received.

[83] Merello starred in La risa es salud by Hugo Moser in 1976[19] and then joined the cast of the Teatro Astros in a theatrical revue led by Adolfo Stray and Thelma Tixou.

[10] She filmed El canto cuenta su historia (1976)[84] and finished out the year at Mar del Plata in a revue with Los Chalchaleros and Mariano Mores.

[10] In 1984, Merello made her last theatrical appearance in Para alquilar balcones as 1/3 of the lead trio with Hugo del Carril and Osvaldo Pacheco.

[69] She made her last film in 1985, Las barras bravas[88] and later that same year won a second Diploma of Merit from the Konex Foundation for recognition as Female Tango Singer.