He is claimed to have been the director of music of the ensemble of the church of Santa Maria Maggiore in 1648 - definitely he is mentioned there beginning in 1657.
He is also supposed to have been offered employment as a director of music for St. Peter in Rome in 1654, but Baini reports Orazio Benevoli to have been the Maestro there at that time.
[6] A severe outbreak of pestilence in 1656 made Pope Alexander VII forbid all public events in Rome.
Despite all that Fabri was made the maestro at Santa Maria Maggiore and in 1657 he advanced to be the director of music of the private chapel of the Borghese family at the same church.
Several compilations of all the composers of that time were edited by Domenico Bianchi, Filippo Beretti, Giovanni Poggioli and especially by Florido de Silvestris.