Piazzolla also wrote the first tango opera, Maria of Buenos Aires, based on a libretto by the poet Horacio Ferrer. At the heart of its surreal plot is the story of an unfortunate girl – Maria – born in a poor suburb of Buenos Aires “on a day when God was drunk”. Heading to downtown Buenos Aires, she is seduced by the music of the tango and becomes a prostitute. Thieves and brothel keepers gathered for a black mass decide she must die. After her death, Maria is condemned to hell, which is effectively the city itself; her shadow now roams the city. She has returned to virginity, is impregnated by the word of the Evil Spirit, and in the presence of three construction workers (a reference to the three Magi of the Bible) and the women who prepare pasta, gives birth to a child Mary, who may be she herself.

The first part of the opera retells the story of the prostitute, the action of the second part takes place after her death. The main characters are Maria( and, after her death, Maria’s shadow), a spider singer (who functions as poet and narrator, a duende similar to a ghoul), and several members of the Buenos Aires underworld: several puppets controlled by the duende, a circus of psychoanalysts, pasta makers, and construction workers. Many elements of the libretto suggest parallels between Maria and Jesus’ mother (Mary), as well as Jesus himself.

The music of “Maria of Buenos Aires” is borrowed from the idiom of the ” tango nuevo” for which Piazzolla was famous.The original idea of his story was suggested by Egle Martin, his mistress at the time, who was married to Eduardo “Lalo” Palacios. Originally, the opera’s title role was intended for Martin, but while Piazzolla was writing the work, the two broke up. This happened after he demanded her hand from her husband at Christmas (1967). According to Martin, Piazzola told Lalo “She is music, she cannot belong to anyone; she is music, and music is me”. After the break-up between the two, the composer desperately needed a female performer to replace Egle Martin. Fortunately, shortly afterwards, at the famous nightclub Nuestro Tiempo, which was once like a home for him, he met the folk singer Amelita Baltar. The similarity between her and Maria’s character, combined with Amelita’s beauty and captivating stage presence, made her perfect for the role.

While it is certainly not ” operatic ballet,” in the strict sense of the word, as the dance is a tango and not a classical ballet, Maria of Buenos Aires falls into the tradition of setting dance pieces as an integral part of an operatic work. For the orchestration, Piazzolla used the quintet that had been working up to that point: Piazzolla (bandoneon), Antonio Agri (violin), Jamie “El Russo” Gossis (piano), Oscar López Ruiz (guitar), and Quicho Díaz (double bass), to which he added viola, cello, flute, percussion, vibraphone and xylophone, and a second guitar. “Maria of Buenos Aires” is often performed with dancers as well as musicians. There are several extant arrangements, including Piazzolla’s original and one by Pablo Ziegler.