Neither Spem in alium, the widely acclaimed 'songe of fortie partes' by Thomas Tallis, nor Alessandro Striggio's forty-part Mass is the largest-scale counterpoint work in Western music. The actual winner is Gregorio Ballabene, a relatively unknown Roman maestro di cappella, a contemporary of Giovanni Paisiello, Joseph Haydn and Luigi Boccherini, who composed in forty-eight parts for twelve choirs. His Mass saw only a public rehearsal and was never performed liturgically despite all of Ballabene's efforts to promote it. On closer inspection, however, the work deserves special consideration as a piece of outstanding combinatory creativity - the product of a talent able to conceive, structure and realise a project of colossal dimensions. It might even be claimed that if Charles Burney had gained knowledge of it, all derogatory comments by nineteenth-century music historians would not have succeeded in extinguishing the interest of later generations. Ballabene's Mass has remained completely unstudied until today, even though the score survives in prominent collections. This study offers, for the first time, a historical and analytical perspective on this overlooked manifestation of a very individual musical intelligence.