Samba-enredo is a sub-genre of Samba in which songs are performed by a samba school (or escola de samba) for the festivities of Carnaval. "Samba-enredo" is the Portuguese equivalent of "samba in song", or "song samba".
Choosing a samba-enredo is a long and tedious process. Before Carnaval, months in advance, a samba school holds contests for writing the song. Each school receives many, sometimes hundreds of songs, hoping to be the next samba-enredo for that year.
They select the song by process of elimination and usually end up somewhere between five and ten songs. Around this time, the "finalist samba-enredos" are played with music and are voted on by the leaders of the samba school and the carnavalesco—the director of the school for Carnaval.
After months of deliberation, the new samba-enredo is chosen and becomes the voice of the samba school for Carnaval. The samba-enredo must be well sung by the samba school's puxador (or singer) or the school will lose points for the scoring and judging for the Carnaval competition. While the puxador sings, everyone marching in the Carnaval parade must sing along with him. Harmony is crucial when singing the samba-enredo.