THE ORUS
Each Orisha or "saint" has its own individual rhythms, which are played exclusively in his or her honor.
The lukumi musical liturgies in Cuba are known as oru. They cosist of a series of hymns dedicated to the diverse Orishas in a ritual order. The sound oru could be the same as oro, which in Yoruba means "word" or "conversation". So, oru is to "speak" with the Orishas.
Santeria has three main liturgies. There is one of unaccompanied singing and chanting. The second, the oru del igbodu, is unaccompanied bata drumming. The third, the oru del eya aranla, is composed of drumming, singing, and dancing.
The singing oru seems to have precedence. It is only used in cryptic rites of operational magic, consecration or sacraments such as initiations and ebos (sacrifices).
The bata oru is also private and is performed in the igbodu, the inner sanctum. It is a series of drummed prayers played before the beginning of all solemn ceremonies and collective dancing, asking the Orishas for permission to hold the ceremony and their participation in it.
When the oru del igbodu ends, the oru del eya aranla, the public ceremony; which takes place outside the inner sanctum, begins. Most of the pieces in this oru are the same as parts of the oru del igbodu.
After that oru, there is the guemilere, in which the rhythms of the eya aranla can be played as desired, without regard to formal order. "Generic" rhythms, such as yakota, are played. The formal ceremonies turn into a celebration. All pieces may be played except for those dedicated to the Eggun, the spirits of the dead.
When the nervous convulsions which precede a possession are noted, the chants are repeated. The phrases and the tempo are speeded up, until one or more participants are "ridden" by an Orisha.
The ceremonies end with a closing oru. These pieces are again played solemnly in a formal order.