I recently discovered that the piece of spoken prose at the beginning of some tangos is called a glosa tanguera or ‘tango glosa’.
A ‘glose’ or glosa is an early Renaissance form developed by poets of the Spanish court in the 14th and 15th centuries. In a glosa, tribute is paid to another poet, and it is made up of two parts, the opening which is referred to as cabeza or ‘texte’ and the second part is the glosa or ‘glose’ itself.
What this means is that four lines of poetry are quoted as an epigraph from another poem or poet. The four lines act a as a refrain in the final line of the four stanzas written by the poet. That is, the first line of the epigraph would be the final line of the first stanza, the second line ends the second stanza, and so on.
In regards to tango, these glosas would be used as a brief commentary of the tango that followed. Interestingly these were not read by the vocalist, but rather by a different artist and it was something that was very common on live radio.
Here are some well known tangos that start with a glosa:
Café Dominguez, Angel D’Agostino, glosa: Julian Centeya
La Cumparsita, Juan D’Arienzo, glosa: Antonio Cantò
Bajo el Cono Azul, Alfredo de Angelis, vocals: Floreal Ruiz, glosa: Néstor Rodi
Nada, Miguel Caló, vocals: Raúl del Mar, glosa: Héctor Gagliardi
Of-course, at a milonga, we don’t always hear these glosas because the DJs either trim them off or they play a different version of the recording that doesn’t include the glosa. Personally, I really enjoy listening to a glosa during a milonga but perhaps I’m biased as I can understand what is being said. I don’t know if the same is true for non-Spanish speakers.