The seis is a type of Puerto Rican dance music, related to décima. It originated in the later half of the 17th century in the southern part of Spain. The word means six, which may have come from the custom of having six couples perform the dance, though many more couples eventually became quite common. Men and women form separate lines down the hall or in an open place of beaten earth, one group facing the other. The lines would approach and cross each other and at prescribed intervals the dancers would tap out the rhythm with their feet.
The melodies and harmonies are simple, usually performed on the cuatro, guitar, and güiro, although other indigenous instruments are used depending on the available musicians. The 2/4 rhythm is maintained by the güiro and guitar.