Casamiento literally translates to "wedding" or "marriage". While "boda" is a more common word for wedding in many Spanish-speaking regions, "casamiento" is a beautiful and slightly more traditional term, often found in folk songs and older texts.
In this song, Violeta Parra uses "casamiento" to set the scene for a very unique and somber wedding where everything, from the participants to the decor, is described as "negro" (black). This choice of word immediately evokes a sense of ceremony and tradition, making the subsequent descriptions of the all-black event even more striking and memorable.
Violeta Parra's "Casamiento de Negros" tells a story that starts with a wedding, but it's not your typical joyful celebration. From the very beginning, everything is described as black: "Negros novios y padrinos, Negros cuñados y suegros" [Black bride and groom and godparents, Black brothers-in-law and in-laws]. Even the priest is black, and the tablecloth at the reception is black. It's a bit funny how insistent the song is on this detail, making you wonder if it's about actual color or something else entirely.
The story continues with the couple going to bed "Debajo de un cielo negro" [Under a black sky]. Things take a sad turn when the bride gets sick. The doctor prescribes "emplasto de barro, Pero del barro más negro" [a mud poultice, But of the blackest mud]. Sadly, the "negrita" [little black woman] dies, and the song ends with a "velorio más negro" [blackest wake], with no candles lit. It's a really stark and almost comically bleak narrative, using the color black to describe every single element of life, love, and loss.