A solis ortus cardine
/ Beatus auctor saeculi
alternates plainchant with polyphony, although in this case the polyphonic verses are based much more closely on the notes of the plainchant hymn than are the polyphonic verses of the Magnificats. The technique of using a plainchant melody stretched out in long notes in one of the lowest voice parts was part of a compositional tradition stretching back for hundreds of years. Praetorius uses the technique (albeit not entirely strictly) to lend an antique feel to this motet’s varied textures.
from notes by Jeremy Summerly © 2008