A new theoretical clarity for the motet arose not from its musical-compositional features, but rather from its textual dimension. In the early fifteenth century, an author of probably German origin attempted to define the motet as a "cantus ecclesiasticus" based solely on the status of its texts. A motet's "function" is largely determined by the circumstances of its commissioning: the institution, occasion, performance conditions, ritual context, and compositional standards. These factors comprise the so-called "complex of expectations" of a particular work. The compositional pluralization of the motet in the fifteenth century was initially focused on this complex of expectations. The early fifteenth century saw a late flourishing of the isorhythmic motet. The growing number of collections that combine Ordinary cycles and motets in the second half of the century testifies to an increasing sacralization of the genre. Psalm composition is inextricably tied to the antiphon, even though this tradition derives from non-psalmic Marian antiphons of the mid-fifteenth century.