The PEM database was established as part of the FCT-funded project "Musical exchanges, 1100-1650: The circulation of early music in Europe and overseas in Iberian and Iberian-related sources" / «Intercâmbios musicais, 1100-1650: A circulação de música antiga na Europa e além-mar em fontes ibéricas ou conexas» (PTDC/EAT-MMU/105624/2008), directed by Manuel Pedro Ferreira at CESEM, NOVA FCSH, between 2010 and 2013.
PEM is a continuation of an earlier project led by M. P. Ferreira entitled "Digital survey of pre-1600 musical sources" / «Levantamento digital de património musical manuscrito (antes de 1600)» (POCTI/EAT/46895/2002), 2005-2008.
PEM is part of the Cantus Index Network and is connected to other international medieval music databases by means of unique Cantus ID numbers. PEM’s instructions for indexing plainchant are based on the rules originally established by the CANTUS Database (now Cantus Manuscript Database), which was the forerunner of online medieval music databases for plainchant sources. However, PEM's instructions expand these rules by integrating other descriptive fields that allow to further specify the codicological features of musical manuscripts. Furthermore, PEM is the first online chant database that started to systematically catalogue and create musical indexes of chants for the Proper of the Mass.