The first mention of the work's publication is in a July 1610 letter by Monteverdi's assistant, Bassano Casola, to Cardinal Ferdinando Gonzaga, the duke's younger son. Casola described that two compositions were in the process to be printed, a six-part mass ("Messa da Capella") on motifs from Nicolas Gombert's "In illo tempore", and psalms for a vespers setting for the Virgin ("Salmi del Vespro della Madonna"). He described the psalms as "varying and diverse inventions and harmonies over a canto fermo" (cantus firmus), and noted that Monteverdi would travel to Rome to personally dedicate the publication to the Pope in the autumn.