The surreal plot centers on a prostitute in Buenos Aires, Argentina; the second half takes place after her death. The characters include María (and, after her death, the Shadow of María), a singer of payadas, various members of the Buenos Aires underworld, a poet narrator who is also a goblin, several marionettes under his control, and a circus of psychoanalysts. Several elements of the libretto suggest parallels between María and Mary, the mother of Jesus (in Spanish, María) or to Jesus himself.
The music draws on the nuevo tango idiom for which Piazzolla is famous. The original idea for the story was conceived by Piazzolla's then lover, Egle Martin (though she was already married to Eduardo "Lalo" Palacios). The title role was originally conceived for Martin, but while Piazzolla was still composing the operita, he and Martin broke up after he asked her husband for her hand at Christmas in 1967. According to Martin Piazzolla said to Lalo: "she is music, she can't belong to anybody, no she is music, she is music, and that's me." After their rift a replacement was desperately needed, but Piazzolla soon met folksinger Amelita Baltar at the Buenos Aires nightclub "Nuestro Tiempo", formerly called "676" and once Piazzolla's home base in Argentina. Baltar's identification with the character Maria paired with her beauty and captivating stage presence made her ideal. The piece is written for at least three vocalists (one of whom, the narrator, speaks rather than singing). For the orchestration Piazzolla augmented his current working quintet: Piazzolla (bandoneon), Antonio Agri (violin), Jamie "El Russo" Gosis (piano), Oscar Lopez Ruiz (guitar) and Enrique "Kicho" Diaz (bass); with viola, cello, flute, percussion, vibraphone and xylophone, and another guitar. Maria de Buenos Aires has often been performed with dancers as well as the musicians. There are several extant arrangements, including Piazzola's own and one by Pablo Ziegler.
On September 26, 2007 Gotham Chamber Opera premieres a new production of MARIA DE BUENOS AIRES at Skirball Center, NYC, with co-choreographers David Parsons and Pablo Pugliese; Parsons Dance participates and mezzo-soprano Nicole Piccolomini portrays Maria.
While certainly not in the narrow sense an opera ballet, because the dance is tango rather than classical ballet, it falls within the tradition of having set dance pieces integral to an operatic work.
The ill-omened María, born "one day when God was drunk" in a poor suburb of Buenos Aires, heads to the center of Buenos Aires, where she is seduced by the music of the tango and becomes a streetwalker. Thieves and brothel keepers, gathered at a black mass resolve her death. After her death, she is condemned to a hell which is the city itself: her Shadow, now walks the city. She has returned to virginity, is impregnated by the word of the goblin poet, and—witnessed by three Construction Worker Magi and The Women Who Knead Pasta—gives birth to a Child María, who may be herself.