The Missa sopra Ecco sì beato giorno is a musical setting of the Ordinary of the Mass, for 40 and 60 voices, by Florentine Renaissance composer Alessandro Striggio. It probably dates from 1565–6, during the reign of his employer, Cosimo I de' Medici. Lost for more than 400 years, it was recently rediscovered in Paris. Most of the mass is for five separate choirs of 8 voices each, with the closing Agnus Dei being for five separate choirs of 12 voices each; all of the voice parts are fully independent. With its huge polychoral forces, climaxing on sixty fully independent parts, it is the largest known polyphonic composition from the entire era. Background The court of the Medici was long known for its patronage of the arts, including music, and the Medici rulers, from Lorenzo the Magnificent to Cosimo I de' Medici, were particularly noted for their love of music. Keenly aware that their status depended on not only employing the most talented artists and musicians, but having them create spectacular works and having them disseminated, they encouraged composers to write music which exceeded that of their contemporaries in size and scope. During the 1530s and 1540s, Francesco Corteccia, who was the principal composer for the first part of Cosimo's reign, wrote series of elaborate intermedii—groups of madrigals designed to be performed between the acts of plays, sung by actors in costume and accompanied by instruments. This musical form was one of the predecessors of opera. In the realm of sacred music, the desire of the Medici for opulence was no less. Instead of decorating plays with madrigals interspersed between the acts, however, the Medici's court composer – who was Striggio by the 1560s – chose to create works for larger groups of voices than had been attempted before, and to accompany these already massive vocal forces with instruments. His first attempt was apparently the Missa sopra Ecco sì beato giorno, and some time later he followed this with a 40-voice motet setting, Ecce beatam lucem, a piece which has long been known. Some other gigantic polychoral works from the same time include Thomas Tallis's famous and often-performed Spem in alium nunquam habui, for 40 voices, which may have been a response to hearing either the motet or the Mass in 1567; Stefano Rossetto's 50-voice motet Consolamini popule meus; and Cristofano Malvezzi's 30-voice intermedio for another Medici marriage, O fortunato