G.B.Costanzi was a much appreciated composer and maestro di cappella in Rome for almost 50 years; he studied with Arcangelo Corelli and had among his own students Luigi Boccherini.
This score, a Miserere for 4 voices in alternatim with gregorian chant, was composed in the years when he was in St.Peter's Cathedral (after 1755).
Transcription by Guido Menestrina from a manuscript in the Spanish National Library.