The eighteenth century Sicilian Prelate, musician and composer Monsignor Antonino Reggio has been described by his contemporaries as 'a man of great intellect, erudite, and very deep in music, eminent for his skill in the art, and learning in the science of sound'. This short monograph highlights one of Reggio's works, a manuscript containing twenty quartets set for three voices. The work is unusually set for three sopranos and a contralto in the 'duetto notturno' style. The current work outlines the history of the three extant manuscripts of the work and considers them in the light of the 'duetto notturno' style. There is a detailed section on the original Metastasio texts, together with a comprehensive bibliography. It is planned to be a companion to the forthcoming critical performance edition, in preparation by the current author. Also it is a prelude to a more comprehensive biography of Reggio currently in preparation. .