Northern Mexico is home to the last singers of Cardenche Song, a nostalgic melody of love, wailing and tragedy.  This is a journey in search of this musical tradition, rooted in cotton farmers and miners now on the verge of extinction.  Cardenche is sung a cappella in groups of three and has been shared from generation to generation. It takes the name of a cactus whose thorn — like love, the Cardenche singers note — goes in too easily but hurts like hell to take out. To Die in the Desert  (A morir a los desiertos) is a dazzling new documentary that features heartbreaking musical performances that capture why this howl of a singing technique is so unique and important.  Directed by Marta Ferrer.