Sweelinck wrote variations on three different categories of sacred melody. They are plainsong melodies, tunes from the Lutheran chorales and Geneva Psalter. Some writers have attempted to codify the differences between the variations on sacred and secular melodies, but similar techniques occur in both groups of works. The notes of the melody are presented as a cantus firmus, usually in the top part, although it can migrate to any other part of the texture – this aspect is perhaps found more in the sacred works. The cantus can be plain or with varying degrees of decoration. Accompanimental material may be derived from the melody and used imitatively or be merely decorative. In plainsong based works, such as Christe qui lux est et dies
the cantus is generally in long notes of equal length, all rhythmic interest being in the accompaniment. Here a three part texture is maintained thoughout the three verses, with the melody moving from the top, to the middle, and then back again, this time twice as fast.
from notes by Stephen Westrop © 2003