Musicologie Médiévale is a hardcore resource for Gregorian chant, medieval musicology and medieval liturgy that goes down all sorts of fun rabbit holes. Lots of academic participants, links to excellent resources for original manuscripts, conferences, institutions, experts, performers, libraries and more. Much of the site is in French and a good bit in English. You can spend hours exploring here… give a donation if you use it, please! We need to support these kinds of projects!