- John Caldwell
A liturgical form in which the organ replaced the odd-numbered or even-numbered stanzas of a plainsong hymn, alternating with the choir. It is convenient to consider other alternatim forms used in the Office at the same time, in particular the Te Deum, Magnificat and Salve regina. Antiphons to psalms and canticles were also set, especially in England, but they are complete in themselves and not in the strict sense alternatim.
The earliest extant music in these forms dates from the early 15th century, but there are earlier references to alternatim singing, especially of the Te Deum. A passage in Dante's Purgatorio (ix.142–5) appears to refer to this. At Essen in the 14th century a triple scheme of alternation was devised for the singing of the Te Deum after the performances of the Easter sepulchre play at Matins: the organ began, the canonesses in whose convent the performance took place sang the second verse, the clerks (men in orders) sang the third, and so on to the end. At St Albans in ...