The manuscripts presented in this book, most of them published for the first time, served different functions. The Vatican sources of the Allegri, CS 205–6 and 340–1 (the latter also containing Bai’s Miserere), were fair copies in choirbook format, made for the use of the Papal Choir. Biordi’s manuscript, CS 263, shows a composer at work, as he completely re-imagines Allegri’s composition. All these give the Miserere unadorned, although it is interesting to see that Biordi added some decorations to the cadences when, having worked on later verses (see verse 13 in Appendix 2), he further modified verse 1.

The earliest source with some decoration, printed in 1767 by Blainville (B), is hard to place. Certain phrases show that its maker must have at least heard the Miserere being sung, although other ornaments hardly even seem Italian. Its purpose as much as its provenance remains for the moment a mystery. However, all subsequent sources with performance indications clearly have their origins in the Vatican, although only Mustafà’s extraordinary manuscript (M) is still there. The earliest, the Manchester manuscript (Man), was put together by members of the Papal Choir for a valued friend, possibly to be used in a private performance. The Paris manuscript (P) was the presentation copy made from it. Although these give only three verses of the Miserere, the exhaustive detail they present gives us a good idea of what Mozart heard in 1770. The manuscript in Milan (Mil) shares the same qualities and also seems to have been a private affair, presented by a papal singer to a friend or acquaintance. The series of manuscripts from the 1820s, now in the British Library and various parts in German-speaking Europe (collectively Source A), must have been created for interested collectors. While we do not know their ultimate source, nothing in them suggests anything other than a close relationship with the Papal Choir. They open a window into certain of its practices but, being focused on the famous abbellimenti, lack much important practical detail. Some of that necessary information was published in 1840 by Alfieri in his introduction, but the music in his edition adds little new information, despite his being an official Vatican publisher.