Gallus Dressler was a German composer and music theorist who served as Kantor in the church school at Magdeburg. Though a few of his works have remained in the choral repertoire, he is best known for his theoretical writings, especially his Praecepta musicae poeticae (MS, 1563), which contains some of the earliest detailed description of the compositional process of the Renaissance motet
Dressler's chief contribution comes to us in this unpublished manuscript, which from its organization and tone may have been his notes for teaching composition classes. As such it is one of the first sources to give in detail a practical approach to the composition of the Renaissance motet. Dressler's explication of musica poetica can be summarized in two principles: the application of the rhetorical principles of exordium, medio, and finis to the structure of a motet, and the application of the grammatical principle of a "clausula" (sentence) to smaller musical units demarcated by cadences.
The modal aspect of Dressler's musical poetics agrees in principle with that of Pietro Pontio and other contemporary theorists, but Dressler takes it a step further by teaching the use of the principal cadences of the given musical mode (cadences to the final and dominant degrees) to assert stability in the exordium and the finis, and cadences to other degree during the medio to provide contrast and interest