The Mass – written to be performed strictly a cappella – entirely fulfilled the aspirations of the “Cecilian Movement” by referring to the renaissance polyphonic models (the “return to early music” so dear to Giuseppe Verdi), reinterpreted though with plasticity and inventiveness. Whilst Tebaldini kept to the guide lines of Gregorian chant, Bossi only took inspiration from it, and created the themes ex novo on which to develop the famous text by Tommaso da Celano (1190 ca.– 1260 ca) and freely harmonized on them. This is particularly apparent in the Hostias et praeces of the Offertorio, at the entry to the Sanctus (haunted by the spirit of Monteverdi), in the Osanna and in the Cum Sanctis tuis that ends with a very powerful sound effect. Successively Bossi also composed the Requiem, Kyrie and Dies Irae, writing an optional organ (or harmonium) part to accompany the voices. The Messa was again performed in this form in the Pantheon, on 14th March 1906 for a ceremony to commemorate King Umberto I.