This work presents a first modern edition of the premier opus of the prominent seventeenthcentury contrapuntist and polemicist, Romano Micheli. Several pieces in original notation, a collection of options for different voicings, and editions for male and female voices are presented. The Roman context and the personal, social and religious factors impacting the composer are investigated. The inclusion of instructions for the use of Micheli’s psalmi by nuns demands investigation of nuns and their music. The analysis of compositional techniques reveals a gradual adaptation of traditional musical language. This sophisticated work uses complex compositional techniques built on the foundations of the ‘Ancient Rigor’ of Renaissance modal counterpoint with added elements of ‘Modern Delight’.