Milonga (danstillställning) – Wikipedia
A tanda is a turn of dancing in a milonga, and by association, a set of pieces of music,
usually between three and five, that is played for one turn.
Most commonly the music is tango, milonga or vals.
The most common style is to play:
4 - four pieces in the tango tandas,
3 - three in the milonga tandas,
3 - three or four in the vals tandas.
A typical order of tandas is:
T-T -V- T-T -M
(T for a tanda of tangos, V for a tanda of vals cruzado, M for a tanda of milongas).
Between tandas is played a cortina (Spanish for "curtains"),
a musical pause to allow dancers to leave the floor and to serve as a short break between tandas.
A cortina (curtain) is a short piece (20–60 seconds) of music that is played between tandas
at a milonga (tango dance event).
The cortina lets the dancers know that the tanda has ended.
The partners can then thank each other and return to their own tables, to find a new dance partner at the next tanda.
Cortinas are used at many of the milongas in Argentina and Uruguay and increasingly elsewhere.
Tandas are normally arranged by feel of the music.