Development, which may have taken place between the years 400 and 800, led to a variety of forms and types for the different items of the chant, each item receiving the structure proper to it from the standpoint of the liturgy. All these forms stem from three original types:
(1) direct psalmody, in which the psalm is sung with no refrain by a soloist or a choir
(2) responsorial psalmody, in which a soloist sings the verse and is answered by a choir
(3) antiphonal psalmody, in which the choir is divided into two groups singing alternately